WO2020192355A1 - Method and system for measuring urban mountain viewing visible range - Google Patents

Abstract

Disclosed are a method and system for measuring an urban mountain viewing visible range. The system comprises the following modules: an overall database scenario construction module for acquiring, by means of actual oblique photography measurement, a digital model including a mountain and an urban region; an observation region full-surface rasterization module for extracting an observation region and rasterizing the surface of the model; an observation point spherical coordinate system creation module for setting an observation point, and creating a spherical coordinate system according to an included angle of lines of sight; an effective mountain projection plane cutting module for cutting, in the spherical coordinate system, out an effective mountain projection plane; a mountain viewing line-of-sight blocking calculation module for generating a mountain viewing line of sight and calculating whether the line of sight is blocked; and a data output and imaging module for outputting data of a mountain viewing visible range and carrying out imaging to generate a mountain viewing visible range map.

Description

一种城市观山可视域的测量方法及***Method and system for measuring visual field of urban mountain viewing 技术领域Technical field

本发明属于城市规划领域，尤其涉及一种城市观山可视域的测量方法及***。The invention belongs to the field of urban planning, and in particular relates to a method and system for measuring the visual domain of urban mountain viewing.

背景技术Background technique

观山可视域，又称观山可视域范围、观山可视度、观山可视率、观山可视因子等，是指山体地形在建成环境中为单个观测者视线所及可看到的地域范围。反映了在建成环境中公众对山体自然景观要素的可视程度，关乎到城市公共生活中的空间感受与舒适程度。在城市规划与设计中，将观山可视域的量化结果作为指标有助于城市规划设计决策，同时也可以作为城市空间布局控制与优化的重要依据。通过优化现状城市空间环境中的观山可视域，可以有效地强化山体景观感知，提升城市空间品质，使得公众在城市中可以“看得见山，望得见水”，在整体上达到城市与自然相和谐的状态。根据城市建成环境中反映某视点视觉感知山体的标准图像，分析测算观山可视域的准确数值是城市规划***门进行观山可视域调控的首要和重要技术环节。Mountain viewing area, also known as mountain viewing field range, mountain viewing visibility, mountain viewing rate, mountain viewing factor, etc., refers to the mountain topography that is within the sight of a single observer in the built environment See the geographic scope. It reflects the public's visibility of the natural mountain landscape elements in the built environment, and relates to the spatial feeling and comfort level of urban public life. In urban planning and design, using the quantitative results of the mountain viewing area as an indicator is helpful to urban planning and design decisions, and can also be used as an important basis for urban spatial layout control and optimization. By optimizing the viewing area of mountain viewing in the current urban space environment, the perception of mountain landscape can be effectively strengthened, and the quality of urban space can be improved, so that the public can "see the mountains and the water" in the city, and reach the city as a whole A state of harmony with nature. According to the standard image that reflects the visual perception of the mountain from a certain viewpoint in the urban built environment, analyzing and calculating the accurate value of the viewing area of the mountain is the first and important technical link for the urban planning and construction department to control the viewing area of the mountain.

现有的观山可视域的测度技术包括现场实地测量技术、街景图片可视域测量技术。现场实地测量技术是指采用带有鱼眼镜头的数码相机，在确定的视点对于开放空间拍摄数码照片作为测算的图像来源，并进一步通过photoshop软件中的通道及色阶调整工具，抠取照片中的山体部分，并通过计算山体部分和图像中其他部分的比例关系，得到观山可视域；街景图片可视域测算技术是指通过在百度街景、腾讯街景等地图网站上进行街景图片采样，基于人工智能图像识别技术，进一步由计算机自动识别出图片中的山体要素，并通过计算机计算单张街景图片中山体要素及除山体要素以外的其他要素的比例关系，得到观山可视域数值。The existing measurement technologies for viewing the mountain visual domain include on-site field measurement technology and street view picture visual domain measurement technology. On-site field measurement technology refers to the use of a digital camera with a fisheye lens to take a digital photo in an open space at a certain point of view as the measured image source, and further use the channel and level adjustment tools in the photoshop software to extract the photo The mountain part of the mountain, and by calculating the ratio of the mountain part and the other parts in the image, the viewable field of the mountain is obtained; the street view picture visual field measurement technology refers to the street view picture sampling on the map websites such as Baidu Street View and Tencent Street View. Based on artificial intelligence image recognition technology, the computer automatically recognizes the mountain elements in the picture, and calculates the proportional relationship between the mountain elements in a single street view picture and other elements except the mountain elements to obtain the value of the mountain view field.

上述方法在其本质上，都属于对场景图像的分析测算，其优点在于其操作简及效率高，可以通过现状照片及街景图像直观地划分出山体要素，并计算山体要素同其他城市要素间的比例得出观山可视域，在单张图像的实际操作上体现出易处理的特点，并可以高效率地进行分析测算。In essence, the above methods all belong to the analysis and calculation of scene images. Their advantages are that their operation is simple and efficient. The mountain elements can be intuitively divided through current photos and street scene images, and the relationship between the mountain elements and other urban elements can be calculated. The ratio can be used to obtain the viewable field of the mountain, which is easy to handle in the actual operation of a single image, and can be analyzed and calculated efficiently.

然而目前三种主要的测算方法同本发明提出的一种城市观山可视域的测量方法相比较，在可进行测算的视点区域上存在局限。在选取测算观山可视域的视点时，对于实地测量技术，实测者选取位置具有一定的主观性，往往会根据现场判断选取合适的点位及视角；而对于街景图片可视域测算技术，街景图片只包含城市街道空间的视觉图像，其数据量不能覆盖城市中等级较低的道路，同时也忽略了城市空间中诸如其他地面、建筑立面及屋顶等潜在可能的观山视点。However, compared with the present invention, the three main measurement methods have limitations in the view point area that can be measured. When selecting the viewpoint of the viewing area of the mountain, for the field measurement technology, the location selected by the surveyor has a certain degree of subjectivity, and often chooses the appropriate point and angle of view based on the on-site judgment; and for the street view picture visual domain measurement technology, Street view images only contain visual images of urban street space, and their data volume cannot cover lower-level roads in the city. At the same time, it ignores potential mountain views in urban space such as other grounds, building facades, and roofs.

发明内容Summary of the invention

发明目的：针对以上问题，本发明提出一种城市观山可视域的测量方法及***，能够在既定城市范围内对包括城市道路、城市街区以内、建筑外立面、建筑屋顶等在内的全域表面作为观察点进行城市观山可视域的测量，避免现有测量技术在观察点选择上的局限 性；通过观察点视野边界创建球体坐标系，在球体坐标系中切割出山体有效投影面，并生成观山视线，并对视线是否被遮挡进行计算，有效地提高了观山可视域地测量精度，避免了传统测量方法精度不高、工作效率低下等问题；输出观山可视域数据并成像，最终生成观山可视域地图，效果较为直观，为城市规划设计地进一步分析和决策提供了基础的理性支撑。Objective of the invention: In view of the above problems, the present invention proposes a method and system for measuring the visual field of urban mountain viewing, which can measure the urban roads, urban blocks, building facades, building roofs, etc. within a given city. The entire surface is used as an observation point to measure the visual field of urban mountain viewing, avoiding the limitations of existing measurement technology in the selection of observation points; creating a spherical coordinate system through the boundary of the observation point field of view, and cutting out the effective projection surface of the mountain in the spherical coordinate system , And generate the view of the mountain, and calculate whether the line of sight is blocked, which effectively improves the measurement accuracy of the view of the mountain and avoids the problems of low accuracy and low work efficiency of traditional measurement methods; output the view of the mountain. The data is combined and imaged, and finally a view of the mountain visual domain map is generated. The effect is relatively intuitive, which provides a basic rational support for further analysis and decision-making in urban planning and design.

技术方案：为实现本发明的目的，本发明所采用的技术方案是：一种城市观山可视域的测量方法，包括如下步骤：Technical solution: In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is: a method for measuring the visual field of urban mountain viewing, including the following steps:

(1)采集并建构包含山体及城市区域的实景三维模型场景；(1) Collect and construct real-life 3D model scenes including mountains and urban areas;

(2)提取观测区域，并对模型表面进行栅格化；(2) Extract the observation area and rasterize the model surface;

(3)设定观察点并根据视线夹角创建球体坐标系；(3) Set the observation point and create a spherical coordinate system according to the angle of sight;

(4)在球体坐标系中切割出山体有效投影面；(4) Cut out the effective projection surface of the mountain in the spherical coordinate system;

(5)生成观山视线，并对视线是否被遮挡进行计算；(5) Generate the sight of the mountain and calculate whether the sight is blocked;

(6)输出观山可视域数据并成像，生成观山可视域地图。(6) Output and image the visual field data of mountain viewing to generate a map of the visual field of mountain viewing.

进一步的，步骤(1)采集并建构包含山体及城市区域的数据库场景，具体方法如下：Further, step (1) collect and construct a database scene including mountains and urban areas, and the specific method is as follows:

(1.1)通过实测获取包含山体及城市区域的倾斜摄影数据(1.1) Obtain tilt photography data including mountain and urban areas through actual measurement

倾斜摄影测量通过在飞行平台上搭载多镜头相机组同时采集1个垂直角度及4个倾斜角度的影像，飞行平台比如多旋翼无人机、固定翼无人机、垂直起降无人机等。Tilt photogrammetry uses a multi-lens camera set on a flying platform to collect images at one vertical angle and four tilt angles at the same time. Flying platforms such as multi-rotor drones, fixed-wing drones, and vertical take-off and landing drones.

(1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型(1.2) Generate a real 3D model based on real image texture according to the acquired oblique photography data

倾斜摄影自动化建模软件几何校正、联合平差、多视影像匹配等一系列处理获得地物全方位信息的数据以生成实景三维模型；自动化建模软件可以是法国DIGINEXT公司研发VirtualGeo软件、美国Pictometry公司的EFSElectronic Field Study软件等。Oblique photography automated modeling software geometric correction, joint adjustment, multi-view image matching and other data processing to obtain all-round information of ground features to generate real-world 3D models; automated modeling software can be the VirtualGeo software developed by the French DIGINEXT company, and the US Pictometry The company’s EFSelectronic Field Study software, etc.

(1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform

SuperMap平台运用LOD(Level of Detail)优化调度，仅占用较少硬件资源，保障稳定的海量数据承载能力，并同时支持直接加载任意剖分类型的倾斜摄影模型，包括.osg/.osgb、.x、.dae、.obj等格式，平台通过生成配置文件功能可将存放在多个文件夹的多个＊.osgb格式的倾斜摄影模型数据生成为＊.scp格式文件，该文件记录了倾斜摄影模型文件的相对路径、名称、***点位置及坐标系信息等模型配置内容，平台通过加载＊.scp格式的三维模型缓存文件的方式，实现了OSGB模型数据的直接批量加载与浏览。The SuperMap platform uses LOD (Level of Detail) to optimize scheduling, occupies less hardware resources, guarantees a stable mass data carrying capacity, and supports direct loading of oblique photography models of any subdivision type, including .osg/.osgb, .x , .Dae, .obj and other formats, the platform can generate multiple *.osgb format oblique photography model data stored in multiple folders into *.scp format files through the configuration file generation function, which records the oblique photography model The relative path, name, insertion point position and coordinate system information of the file and other model configuration content, the platform realizes the direct bulk loading and browsing of OSGB model data by loading the *.scp format 3D model cache file.

进一步的，步骤(2)提取观测区域，并对模型表面进行栅格化，具体方法如下：Further, in step (2), the observation area is extracted and the model surface is rasterized. The specific method is as follows:

(2.1)观测区域提取，在SuperMap平台加载倾斜摄影获得的实景三维模型中提取观测区域，此处是从大区域中选择所要观测的区域，从观测区域观测山体。(2.1) Observation area extraction, extract the observation area from the real 3D model obtained by loading the oblique photography on the SuperMap platform, here is to select the area to be observed from the large area, and observe the mountain from the observation area.

(2.2)对实景三维模型中的观测区域表面整体栅格化，栅格的方法是对实景三维模型中的三维城市模型的包括地面、建筑立面、屋顶以单位平方米进行栅格化，在栅格转化的过程中，栅格单元的尺寸选择是非常关键的：栅格单元尺寸过大，则分析精度下降；反之，栅格单元尺寸过小，则后续的可视域分析时间消耗代价将上升。因此，需要根据收集到的数据体量、数据精度及目标分析精度来综合确定栅格基本单元的大小。实际操作中，比如可以选择单位平方米为基本单元精度。(2.2) Rasterize the surface of the observation area in the real 3D model as a whole. The grid method is to rasterize the ground, building facade, and roof of the 3D city model in the real 3D model in units of square meters. In the process of raster conversion, the selection of the size of the raster unit is very critical: if the size of the raster unit is too large, the analysis accuracy will be reduced; on the contrary, if the size of the raster unit is too small, the subsequent visual field analysis time will cost rise. Therefore, it is necessary to comprehensively determine the size of the basic grid cell based on the collected data volume, data accuracy and target analysis accuracy. In actual operation, for example, the unit square meter can be selected as the basic unit accuracy.

进一步的，步骤(3)设定观察点并根据视线夹角创建球体坐标系，具体方法如下：Further, step (3) sets the observation point and creates a spherical coordinate system according to the angle of the line of sight. The specific method is as follows:

(3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as a representative observation point of the grid;

(3.2)创建球体坐标系。将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点。其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度。以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径，作可视半球面，将该半球面定义为标准投影面P _s。以观察点Ο(x _o,y _o,z _o)为球心，分别以地理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

所述当前环境可以是当前空气、阳光等环境。 (3.2) Create a spherical coordinate system. Urban space into viewer viewing point three-dimensional space _{Ο (x o, y o,} z o), i.e. observation grid points. Among them, (x _o , y _o ) is the plane coordinate value of the observer, and z _o is the horizontal plane height of the observation point. Taking the horizontal plane V _h at the height of the observation point as the plane, and the maximum visible distance R _vmax in the current environment as the radius, the visible hemisphere is defined as the standard projection surface P _s . Take the observation point Ο (x _o , y _o , z _o ) as the center of the sphere, and use the true north direction in the geographic coordinate system and the vertical direction of the horizontal plane V _h as the vector bases to establish a spherical coordinate system

The current environment may be the current environment such as air and sunlight.

(3.3)确定视野边界。设定观察点Ο的观察范围受到障碍物或者其他客观原因的限制，造成在该观察点的观察者只能观察到某个角度范围内的景观。这个角度范围被定义为视野边界。记该视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Determine the boundary of the field of view. The observation range of the set observation point Ο is restricted by obstacles or other objective reasons, so that the observer at the observation point can only observe the landscape within a certain angle range. This angular range is defined as the field of view boundary. Record the angle values α _o and β _o between the boundary of the field of view and the vector base in the north direction of the spherical coordinate system.

例如，某观察点的视野范围为正北方到正南方之间，那么该观察点的属性值为(0,π)。For example, if the field of view of an observation point is between true north and true south, the attribute value of the observation point is (0,π).

进一步的，步骤(4)在球体坐标系中切割出山体有效投影面，具体方法如下：Further, step (4) cuts out the effective projection surface of the mountain in the spherical coordinate system, and the specific method is as follows:

在该球面坐标系下，过点(R _vmax,0,α _o)和(0,0,0)作与水平面V _h垂直的平面

同理，过点(R _vmax,0,β _o)和(0,0,0)作与水平面V _h的平面

将标准投影面P _S被平面

和平面

切割出的区域定义为标准有效投影区域P _e。作山体在标准有效投影区域P _e上的投影，该投影为标准有效山体投影。 In this spherical coordinate system, the crossing points (R _vmax ,0,α _o ) and (0,0,0) are planes perpendicular to the horizontal plane V _h

In the same way, the crossing points (R _vmax ,0,β _o ) and (0,0,0) are used as the plane with the horizontal plane V _h

The standard projection plane P _S is plane

And plane

The cut area is defined as the standard effective projection area P _e . Make the projection of the hill on the standard effective projection area P _e , which is the standard effective hill projection.

应该注意的是，由于复杂曲面投影到球面这一过程计算量的限制，在实际应用中，往往会对标准投影面作一定程度上的近似。在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

其中同时r _t为该点到观察点的距离，

该点与观察点连线与正北方方向坐标轴的夹角。取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))。若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面。在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea。对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 It should be noted that due to the limitation of calculation amount in the process of projecting complex curved surfaces onto spherical surfaces, in practical applications, standard projection surfaces are often approximated to a certain extent. In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

Where r _t is the distance from the point to the observation point,

The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction. Take the angular bisector of the visual field boundary of the observation point on the horizontal plane V _h , which intersects the standard projection plane P _s at the point (R _vmax ,0,0.5(α _o +β _o )). If r _t ≥ R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) is used as a plane P _a tangent to the standard projection plane P _s , then P _a is an approximate projection plane; if r _t <R _vmax , then take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is an approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min(R _vmax ,r _t ),0,β _o ) to make straight lines perpendicular to the horizontal plane V _h respectively, Then the area cut by the two straight lines of the approximate projection plane P _a is the approximate effective projection area P _ea . For the area above 2/3 of the height of the mountain, make its projection on the approximate effective projection area P _ea , which is an approximate effective mountain projection.

进一步的，步骤(5)生成观山视线，并对视线是否被遮挡进行计算，具体方法如下：Further, step (5) generates the sight line of the mountain, and calculates whether the sight line is blocked, the specific method is as follows:

(5.1)生成观山视线(5.1) Generating mountain sight

使用近似有效投影区域P _ea上的投影来阐述下面的步骤。将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}。其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量。观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s。另外，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1。若需要对山体上标志性景观进行强调，则可以将与山体上标志性景观相关的点集的权重提高，若不需要，一般地，认为w ₁＝w ₂＝…＝w _s＝1。基本栅格单元 的大小需要根据计算环境、数据质量、精度需求进行综合考虑。 Use the projection on the approximate effective projection area P _ea to illustrate the following steps. The effective mountain projection is rasterized in m×n rectangular grid areas, with the grid center point in the lower left corner as the origin, an orthogonal coordinate system ζ is established on the approximate effective projection area P _ea , and the rasterized The effective hill projection is simplified as a point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} formed by the center points of these grids. Among them, (x ₁ , y ₁ ), (x ₂ , y ₂ ),..., (x _s , y _s ) are the discrete points in the two-dimensional orthogonal coordinate system ζ after the mountain projection rasterized into a point set Coordinates, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid. The line connecting the observation point Ο to the points N ₁ , N ₂ ,..., N _s is recorded as the line of sight L ₁ , L ₂ ,..., L _s . Further, the center point of each grid ownership weight w _i, wherein, 0≤w _i ≤1. If it is necessary to emphasize the iconic landscape on the mountain, the weight of the point set related to the iconic landscape on the mountain can be increased. If not, generally, w ₁ =w ₂ =...=w _s =1. The size of the basic grid unit needs to be considered comprehensively according to the computing environment, data quality, and accuracy requirements.

(5.2)视线遮挡计算(5.2) Sight occlusion calculation

对视线有是否被遮挡进行计算，定义一种成为二分视线计算的算法，该算法的步骤为：Calculate whether the line of sight is occluded, and define an algorithm called bisection line of sight calculation. The steps of the algorithm are:

步骤一：step one:

对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； For the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} to retrieve the point with the abscissa of 0, record the retrieved The subset of points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the ordinate with an abscissa of 0 is the largest The point of is N _0max , and y _0max is the value of the ordinate of N _0max ;

步骤二：Step two:

判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., N s ( x _s ,y _s )} the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

步骤三：Step three:

以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),…,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree is every Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point;

步骤四：Step 4:

每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Every time a node is traversed, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历。In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked.

步骤五：Step Five:

对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值。判断点N _kmax对应的视线L _kmax否被遮挡。若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡。若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四。 For the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )} in the point set with the abscissa k to search, where 0< k≤m, record the subset of retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the total number of points with the abscissa k, mark The point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax . N _kmax determination points corresponding to whether the line of sight L _kmax is blocked. If the line of sight L _kmax is blocked, set all the abscissas in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} to k The line of sight corresponding to the point of is recorded as blocked. If the line of sight L _kmax is not blocked, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to establish a balanced binary search tree, and each of the balanced binary search trees The value of each node is the value of the ordinate of each point in the set. The nodes in the balanced binary search tree are traversed, and step four is executed.

步骤六：分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6: Take k=1, k=2,...,k=m respectively, repeat step 5 to complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.

进一步的，步骤(6)输出观山可视域数据并成像，生成观山可视域地图，具体方法如下：Further, step (6) output and image the viewable field data of the mountain to generate the viewable field map, the specific method is as follows:

(6.1)计算观山可视域数值(6.1) Calculate the value of the view field

对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1。定义一个MVF值，

MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率。 Line of sight _{L i ∈ {L 1, L} 2, ..., L s}, if L _i is flagged as being occluded, the given attribute value L _i μ _i = 0, L _i is marked as not blocked, then imparting L _{The i} attribute value μ _i =1. Define an MVF value,

The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints.

(6.2)通过颜色成像(6.2) Imaging by color

将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值。另外，设置渐变色条，如以绿色对应1完全看到，以白色代表0完全看不到，根据MVF值的大小析出颜色，经过计算机计算，可对三维地图上多个观察区域进行以观山可视率为特征的颜色渲染，即根据MVF值设置观测点对应栅格的颜色，MVF值越大颜色越深，MVF值越小颜色越浅。Set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, and you can calculate the value of mountain visibility in real time. In addition, set the gradient color bar, such as green corresponding to 1 to see completely, and white to represent 0 completely invisible. Colors are precipitated according to the size of the MVF value. After computer calculation, multiple observation areas on the three-dimensional map can be viewed. Visibility is a characteristic color rendering, that is, the color of the grid corresponding to the observation point is set according to the MVF value. The larger the MVF value, the darker the color, and the smaller the MVF value, the lighter the color.

(6.3)生成观山可视域地图(6.3) Generate a view of the mountain visual domain map

将富有MVF值颜色属性的观测区域模型重新置入整体的数据库场景，即将上述着色后的颜色栅格放进原来的模型对应的位置。The observation area model with rich MVF value color attributes is re-placed into the overall database scene, that is, the colored grid is placed in the position corresponding to the original model.

优选的，本专利可补充大气能见度约束。记某城市大气能见度数值为a，若某射线距离大于a，则该射线直接记为有物体遮挡。Preferably, this patent can supplement atmospheric visibility constraints. Record the atmospheric visibility value of a city as a. If the distance of a certain ray is greater than a, the ray is directly recorded as obscured by an object.

此外，本发明还提出一种城市观山可视域的测量***，该***包括如下模块：In addition, the present invention also provides a system for measuring the visual domain of urban mountain viewing, which includes the following modules:

整体场景建构模块，采集并建构包含山体及城市区域的实景三维模型场景；The overall scene construction module, which collects and constructs real 3D model scenes including mountains and urban areas;

观测区域全表面栅格化模块，提取观测区域，并对模型表面进行栅格化；The full surface rasterization module of the observation area extracts the observation area and rasterizes the model surface;

观察点球面坐标系创建模块，设定观察点并根据视野边界创建球体坐标系；Observation point spherical coordinate system creation module, set the observation point and create a spherical coordinate system according to the field of view boundary;

山体有效投影面切割模块，在球体坐标系中切割出山体有效投影面；Mountain effective projection surface cutting module, cut out the effective projection surface of the mountain in the spherical coordinate system;

观山视线遮挡计算模块，生成观山视线，并对视线是否被遮挡进行计算；The mountain sight occlusion calculation module generates the sight line of the mountain and calculates whether the sight line is blocked;

数据输出及成像模块，输出观山可视域数据并成像，生成观山可视域地图。The data output and imaging module outputs and images the viewable field data of the mountain to generate a map of the viewable field.

进一步的，所述整体场景建构模块的具体功能如下：Further, the specific functions of the overall scene construction module are as follows:

(1.1)通过实测获取包含山体及城市区域的倾斜摄影数据；(1.1) Obtain oblique photography data including mountains and urban areas through actual measurement;

(1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型；(1.2) According to the acquired oblique photographic data, a real 3D model based on real image texture is generated;

(1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型。(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform.

进一步的，所述观测区域全表面栅格化模块具体功能如下：Further, the specific functions of the full-surface rasterization module of the observation area are as follows:

(2.1)观测区域提取，在SuperMap平台加载倾斜摄影获得的实景三维模型中提取观测区域以观测山体；(2.1) Observation area extraction, extract the observation area from the real three-dimensional model obtained by loading oblique photography on the SuperMap platform to observe the mountain;

(2.2)对实景三维模型中的观测区域表面整体栅格化。(2.2) Rasterize the entire surface of the observation area in the real three-dimensional model.

进一步的，所述的观察点球面坐标系创建模块具体功能如下：Further, the specific functions of the observation point spherical coordinate system creation module are as follows:

(3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as a representative observation point of the grid;

(3.2)创建球体坐标系，将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点，其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度，以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径，作可视半球面，将该半球面定义为标准投影面P _s，以观察点Ο(x _o,y _o,z _o)为球心，分别以地 理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

(3.2) create a sphere coordinate system, the urban space into viewer viewpoint three-dimensional space _{Ο (x o, y o,} z o), i.e. grid points observed, where, (x _o, y _o ) Is the coordinate value of the plane where the observer is, z _o is the height of the horizontal plane of the observation point, the horizontal plane V _h at the height of the observation point is the plane, and the maximum visible distance R _vmax in the current environment is the radius, which is the visible hemisphere , the hemispherical surface is defined as a standard projection plane P _s, to the viewpoint _{Ο (x o, y o,} z o) is the center of the sphere, respectively, the geographic coordinate system and perpendicular to the direction of true north direction is the horizontal vector V _h Base, establish a spherical coordinate system

(3.3)记该观察点的视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Record the angle values α _o and β _o between the field of view boundary of the observation point and the vector base in the north direction of the spherical coordinate system.

进一步的，所述的山体有效投影面切割模块的具体功能如下：Further, the specific functions of the effective projection surface cutting module of the mountain are as follows:

在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

其中同时r _t为该点到观察点的距离，

该点与观察点连线与正北方方向坐标轴的夹角，取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))，若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面，在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea，对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

Where r _t is the distance from the point to the observation point,

The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction is taken as the angular bisector of the viewing boundary of the observation point on the horizontal plane V _h . The angular bisector intersects the standard projection plane P _s at the point (R _vmax , 0,0.5(α _o +β _o )), if r _t ≥R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) will be the plane P _a tangent to the standard projection plane P _s , Then P _a is the approximate projection plane; if r _t <R _vmax , take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is the approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min (R _vmax ,r _t ),0,β _o ) is a straight line perpendicular to the horizontal plane V _h , then the approximate projection plane P _a is cut by the two straight lines as the approximate effective projection area P _ea , which is 2/3 of the height of the mountain The above area is taken as its projection on the approximate effective projection area _Pea , which is an approximate effective hill projection.

进一步的，所述的观山视线遮挡计算模块的具体功能如下：Further, the specific functions of the mountain view occlusion calculation module are as follows:

(5.1)生成观山视线，将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}，其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量，观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1； (5.1) Generate the view of the mountain, rasterize the effective mountain projection into m×n rectangular grid areas, take the grid center point in the lower left corner as the origin, and establish an orthogonal coordinate system on the approximate effective projection area P _ea ζ, the effective hill projection after rasterization is simplified to a point set composed of the center points of these grids {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s ( x _s ,y _s )}, where (x ₁ ,y ₁ ),(x ₂ ,y ₂ ),...,(x _s ,y _s ) are the points after the hill projection rasterized into a point set in two dimensions Discrete coordinates on the orthogonal coordinate system ζ, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid, observation point Ο to point N ₁ ,N The connection of ₂ ,...,N _s is denoted as the line of sight L ₁ ,L ₂ ,...,L _s . The center point of each grid has a weight w _i , where 0≤w _i ≤1;

(5.2)视线遮挡计算(5.2) Sight occlusion calculation

步骤一，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； Step ₁ : Search for the point with the abscissa of 0 in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, record The subset of the retrieved points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the abscissa is 0 The point with the largest ordinate is N _0max , and y _0max is the value of N _0max ordinate;

步骤二，判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； Step two, N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., In N _s (x _s ,y _s )}, the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

步骤三，以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Step 3: Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point in the set;

步骤四，每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Step 4: When traversing a node, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历；In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked;

步骤五，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值，判断点N _kmax对应的视线L _kmax是否被遮挡，若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡；若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四； Step 5: Retrieve the point with the abscissa of k in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, where , 0<k≤m, record the subset of the retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the point of the abscissa k In total, the point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax ordinate. It is judged whether the line of sight L _kmax corresponding to the point N _kmax is blocked. If the line of sight L _kmax is blocked, the point set {N ₁ ( x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )), the line of sight corresponding to all points with the abscissa k is recorded as occluded; if the line of sight L _{kmax is} not If it is occluded, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to build a balanced binary search tree, and the value of each node in the balanced binary search tree Is the value of the ordinate of each point in the set, traverse the nodes in the balanced binary search tree, and perform step four;

步骤六，分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6, respectively take k=1, k=2,...,k=m, repeat step 5, complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.

进一步的，所述数据输出及成像模块的具体功能如下：Further, the specific functions of the data output and imaging module are as follows:

(6.1)计算观山可视域数值，对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1，定义一个MVF值，

MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率； (6.1) Calculate the value of the viewable field of the mountain. For the line of sight L _i ∈ {L ₁ ,L ₂ ,...,L _s }, if _Li is marked as occluded, the attribute value of L _i is assigned μ _i = 0, L _i is marked as not blocked, the attribute value imparting L _i μ _i = 1, define a value MVF,

The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints;

(6.2)通过颜色成像，将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值，根据MVF值的大小设置观测点对应栅格的颜色；(6.2) Through color imaging, set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, you can calculate the value of mountain visibility in real time, and set the observation according to the MVF value The point corresponds to the color of the grid;

(6.3)生成观山可视域地图，即将上述着色后的颜色栅格放进原模型中对应的位置。(6.3) Generate a view of the mountain visual domain map, that is, put the colored grid into the corresponding position in the original model.

有益效果：与现有技术相比，本发明的技术方案具有以下有益技术效果：Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

本发明提出的一种城市观山可视域的测量方法，能够在既定城市范围内对包括城市道路、城市街区以内、建筑外立面、建筑屋顶等在内的全域表面作为观察点进行城市观山可视域的测量，避免现有测量技术在观察点选择上的局限性；通过观察点视野边界创建球体坐标系，在球体坐标系中切割出山体有效投影面，并生成观山视线，并对视线是否被遮挡进行计算，有效地提高了观山可视域地测量精度，避免了传统测量方法精度不高、工作效率低下等问题；输出观山可视域数据并成像，最终生成观山可视域地图，效果较为直观，为城市规划设计地进一步分析和决策提供了基础的理性支撑。The present invention proposes a method for measuring the visual field of urban mountain viewing, which can perform urban observations on the entire surface including urban roads, urban blocks, building facades, building roofs, etc. within a given city. The measurement of the mountain visual field avoids the limitations of the existing measurement technology in the selection of observation points; the spherical coordinate system is created through the boundary of the observation point field of view, and the effective projection surface of the mountain is cut out in the spherical coordinate system, and the mountain sight line is generated, and Calculate whether the line of sight is blocked or not, which effectively improves the measurement accuracy of the viewing area of the mountain and avoids the problems of low accuracy and low work efficiency of traditional measurement methods; output and image the data of the viewing area, and finally generate the view of the mountain The visual domain map is more intuitive and provides a basic rational support for further analysis and decision-making in urban planning and design.

附图说明Description of the drawings

图1是本发明的城市观山可视域数字化测度方法技术流程图；Figure 1 is a technical flow chart of the digital measurement method for urban mountain viewing in the visual domain of the present invention;

图2是本发明的根据视线夹角创建球体坐标系图；Figure 2 is a diagram of creating a sphere coordinate system according to the angle of sight of the present invention;

图3是本发明的切割山体有效投影面图；Figure 3 is an effective projection plane view of the cutting mountain of the present invention;

图4是本发明的计算观山视线遮挡程度图。Fig. 4 is a diagram of calculating the degree of obstruction of the view of the mountain in the present invention.

具体实施方式detailed description

下面结合附图和实施例对本发明的技术方案作进一步的说明。The technical scheme of the present invention will be further described below in conjunction with the drawings and embodiments.

本发明公开了一种城市观山可视域的测量方法，该方法包括如下步骤：The invention discloses a method for measuring the visual domain of urban mountain viewing, which includes the following steps:

(1)采集并建构包含山体及城市区域的实景三维模型场景；(1) Collect and construct real-life 3D model scenes including mountains and urban areas;

(2)提取观测区域，并对模型表面进行栅格化；(2) Extract the observation area and rasterize the model surface;

(3)设定观察点并根据视线夹角创建球体坐标系；(3) Set the observation point and create a spherical coordinate system according to the angle of sight;

(4)在球体坐标系中切割出山体有效投影面；(4) Cut out the effective projection surface of the mountain in the spherical coordinate system;

(5)生成观山视线，并对视线是否被遮挡进行计算；(5) Generate the sight of the mountain and calculate whether the sight is blocked;

(6)输出观山可视域数据并成像，生成观山可视域地图。(6) Output and image the visual field data of mountain viewing to generate a map of the visual field of mountain viewing.

进一步的，步骤(1)采集并建构包含山体及城市区域的数据库场景，具体方法如下：Further, step (1) collect and construct a database scene including mountains and urban areas, and the specific method is as follows:

(1.1)通过实测获取包含山体及城市区域的倾斜摄影数据(1.1) Obtain tilt photography data including mountain and urban areas through actual measurement

倾斜摄影测量通过在飞行平台上搭载多镜头相机组同时采集1个垂直角度及4个倾斜角度的影像，飞行平台比如多旋翼无人机、固定翼无人机、垂直起降无人机等。Tilt photogrammetry uses a multi-lens camera set on a flying platform to collect images at one vertical angle and four tilt angles at the same time. Flying platforms such as multi-rotor drones, fixed-wing drones, and vertical take-off and landing drones.

(1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型(1.2) Generate a real 3D model based on real image texture according to the acquired oblique photography data

倾斜摄影自动化建模软件几何校正、联合平差、多视影像匹配等一系列处理获得地物全方位信息的数据以生成实景三维模型；自动化建模软件可以是法国DIGINEXT公司研发VirtualGeo软件、美国Pictometry公司的EFSElectronic Field Study软件等。Oblique photography automated modeling software geometric correction, joint adjustment, multi-view image matching and other data processing to obtain all-round information of ground features to generate real-world 3D models; automated modeling software can be the VirtualGeo software developed by the French DIGINEXT company, and the US Pictometry The company’s EFSelectronic Field Study software, etc.

(1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform

SuperMap平台运用LOD(Level of Detail)优化调度，仅占用较少硬件资源，保障稳定的海量数据承载能力，并同时支持直接加载任意剖分类型的倾斜摄影模型，包括.osg/.osgb、.x、.dae、.obj等格式，平台通过生成配置文件功能可将存放在多个文件夹的多个＊.osgb格式的倾斜摄影模型数据生成为＊.scp格式文件，该文件记录了倾斜摄影模型文件的相对路径、名称、***点位置及坐标系信息等模型配置内容，平台通过加载＊.scp格式的三维模型缓存文件的方式，实现了OSGB模型数据的直接批量加载与浏览。The SuperMap platform uses LOD (Level of Detail) to optimize scheduling, occupies less hardware resources, guarantees a stable mass data carrying capacity, and supports direct loading of oblique photography models of any subdivision type, including .osg/.osgb, .x , .Dae, .obj and other formats, the platform can generate multiple *.osgb format oblique photography model data stored in multiple folders into *.scp format files through the configuration file generation function, which records the oblique photography model The relative path, name, insertion point position and coordinate system information of the file and other model configuration content, the platform realizes the direct bulk loading and browsing of OSGB model data by loading the *.scp format 3D model cache file.

进一步的，步骤(2)提取观测区域，并对模型表面进行栅格化，具体方法如下：Further, in step (2), the observation area is extracted and the model surface is rasterized. The specific method is as follows:

(2.1)观测区域提取，在SuperMap平台加载倾斜摄影获得的实景三维模型中提取观测区域，此处是从大区域中选择所要观测的区域，从观测区域观测山体。(2.1) Observation area extraction, extract the observation area from the real 3D model obtained by loading the oblique photography on the SuperMap platform, here is to select the area to be observed from the large area, and observe the mountain from the observation area.

(2.2)对实景三维模型中的观测区域表面整体栅格化，栅格的方法是对实景三维模型中的三维城市模型的包括地面、建筑立面、屋顶以单位平方米进行栅格化，在栅格转化的过程中，栅格单元的尺寸选择是非常关键的：栅格单元尺寸过大，则分析精度下降；反之，栅格单元尺寸过小，则后续的可视域分析时间消耗代价将上升。因此，需要根据收集到的数据体量、数据精度及目标分析精度来综合确定栅格基本单元的大小。实际操作中，比如可以选择单位平方米为基本单元精度。(2.2) Rasterize the surface of the observation area in the real 3D model as a whole. The grid method is to rasterize the ground, building facade, and roof of the 3D city model in the real 3D model in units of square meters. In the process of raster conversion, the selection of the size of the raster unit is very critical: if the size of the raster unit is too large, the analysis accuracy will be reduced; on the contrary, if the size of the raster unit is too small, the subsequent visual field analysis time will cost rise. Therefore, it is necessary to comprehensively determine the size of the basic grid cell based on the collected data volume, data accuracy and target analysis accuracy. In actual operation, for example, the unit square meter can be selected as the basic unit accuracy.

进一步的，步骤(3)设定观察点并根据视线夹角创建球体坐标系，具体方法如下：Further, step (3) sets the observation point and creates a spherical coordinate system according to the angle of the line of sight. The specific method is as follows:

(3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as a representative observation point of the grid;

(3.2)创建球体坐标系。将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点。其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度。以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径， 作可视半球面，将该半球面定义为标准投影面P _s。以观察点Ο(x _o,y _o,z _o)为球心，分别以地理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

所述当前环境可以是当前空气、阳光等环境。 (3.2) Create a spherical coordinate system. Urban space into viewer viewing point three-dimensional space _{Ο (x o, y o,} z o), i.e. observation grid points. Among them, (x _o , y _o ) is the plane coordinate value of the observer, and z _o is the horizontal plane height of the observation point. Taking the horizontal plane V _h at the height of the observation point as the plane, and the maximum visible distance R _vmax in the current environment as the radius, the visible hemisphere is defined as the standard projection surface P _s . Take the observation point Ο (x _o , y _o , z _o ) as the center of the sphere, and use the true north direction in the geographic coordinate system and the vertical direction of the horizontal plane V _h as the vector bases to establish a spherical coordinate system

The current environment may be the current environment such as air and sunlight.

(3.3)确定视野边界。设定观察点Ο的观察范围受到障碍物或者其他客观原因的限制，造成在该观察点的观察者只能观察到某个角度范围内的景观。这个角度范围被定义为视野边界。记该视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Determine the boundary of the field of view. The observation range of the set observation point Ο is restricted by obstacles or other objective reasons, so that the observer at the observation point can only observe the landscape within a certain angle range. This angular range is defined as the field of view boundary. Record the angle values α _o and β _o between the boundary of the field of view and the vector base in the north direction of the spherical coordinate system.

例如，某观察点的视野范围为正北方到正南方之间，那么该观察点的属性值为(0,π)。For example, if the field of view of an observation point is between true north and true south, the attribute value of the observation point is (0,π).

进一步的，步骤(4)在球体坐标系中切割出山体有效投影面，具体方法如下：Further, step (4) cuts out the effective projection surface of the mountain in the spherical coordinate system, and the specific method is as follows:

在该球面坐标系下，过点(R _vmax,0,α _o)和(0,0,0)作与水平面V _h垂直的平面

同理，过点(R _vmax,0,β _o)和(0,0,0)作与水平面V _h的平面

将标准投影面P _s被平面

和平面

切割出的区域定义为标准有效投影区域P _e。作山体在标准有效投影区域P _e上的投影，该投影为标准有效山体投影。 In this spherical coordinate system, the crossing points (R _vmax ,0,α _o ) and (0,0,0) are planes perpendicular to the horizontal plane V _h

In the same way, the crossing points (R _vmax ,0,β _o ) and (0,0,0) are used as the plane with the horizontal plane V _h

The standard projection plane P _s is plane

And plane

The cut area is defined as the standard effective projection area P _e . Make the projection of the hill on the standard effective projection area P _e , which is the standard effective hill projection.

应该注意的是，由于复杂曲面投影到球面这一过程计算量的限制，在实际应用中，往往会对标准投影面作一定程度上的近似。在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

其中同时r _t为该点到观察点的距离，

该点与观察点连线与正北方方向坐标轴的夹角。取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))。若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面。在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea。对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 It should be noted that due to the limitation of calculation amount in the process of projecting complex curved surfaces onto spherical surfaces, in practical applications, standard projection surfaces are often approximated to a certain extent. In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

Where r _t is the distance from the point to the observation point,

The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction. Take the angular bisector of the visual field boundary of the observation point on the horizontal plane V _h , which intersects the standard projection plane P _s at the point (R _vmax ,0,0.5(α _o +β _o )). If r _t ≥ R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) is used as a plane P _a tangent to the standard projection plane P _s , then P _a is an approximate projection plane; if r _t <R _vmax , then take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is an approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min(R _vmax ,r _t ),0,β _o ) to make straight lines perpendicular to the horizontal plane V _h respectively, Then the area cut by the two straight lines of the approximate projection plane P _a is the approximate effective projection area P _ea . For the area above 2/3 of the height of the mountain, make its projection on the approximate effective projection area P _ea , which is an approximate effective mountain projection.

进一步的，步骤(5)生成观山视线，并对视线是否被遮挡进行计算，具体方法如下：Further, step (5) generates the sight line of the mountain, and calculates whether the sight line is blocked, the specific method is as follows:

(5.1)生成观山视线(5.1) Generating mountain sight

使用近似有效投影区域P _ea上的投影来阐述下面的步骤。将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}。其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量。观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s。另外，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1。若需要对山体上标志性景观进行强调，则可以将与山体上标志性景观相关的点集的权重提高，若不需要，一般地，认为w ₁＝w ₂＝…＝w _s＝1。基本栅格单元的大小需要根据计算环境、数据质量、精度需求进行综合考虑。 Use the projection on the approximate effective projection area P _ea to illustrate the following steps. The effective mountain projection is rasterized in m×n rectangular grid areas, with the grid center point in the lower left corner as the origin, an orthogonal coordinate system ζ is established on the approximate effective projection area P _ea , and the rasterized The effective hill projection is simplified as a point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} formed by the center points of these grids. Among them, (x ₁ , y ₁ ), (x ₂ , y ₂ ),..., (x _s , y _s ) are the discrete points in the two-dimensional orthogonal coordinate system ζ after the mountain projection rasterized into a point set Coordinates, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid. The line connecting the observation point Ο to the points N ₁ , N ₂ ,..., N _s is recorded as the line of sight L ₁ , L ₂ ,..., L _s . Further, the center point of each grid ownership weight w _i, wherein, 0≤w _i ≤1. If it is necessary to emphasize the iconic landscape on the mountain, the weight of the point set related to the iconic landscape on the mountain can be increased. If not, generally, w ₁ =w ₂ =...=w _s =1. The size of the basic grid unit needs to be considered comprehensively according to the computing environment, data quality, and accuracy requirements.

(5.2)视线遮挡计算(5.2) Sight occlusion calculation

对视线有是否被遮挡进行计算，定义一种成为二分视线计算的算法，该算法的步 骤为：Calculate whether the line of sight is occluded, and define an algorithm called a binary line of sight calculation. The steps of the algorithm are:

步骤一：step one:

对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； For the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} to retrieve the point with the abscissa of 0, record the retrieved The subset of points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the ordinate with an abscissa of 0 is the largest The point of is N _0max , and y _0max is the value of the ordinate of N _0max ;

步骤二：Step two:

判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., N s ( x _s ,y _s )} the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

步骤三：Step three:

以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),…,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree is every Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point;

步骤四：Step 4:

每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Every time a node is traversed, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历。In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked.

步骤五：Step Five:

对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值。判断点N _kmax对应的视线L _kmax否被遮挡。若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡。若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四。 For the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )} in the point set with the abscissa k to search, where 0< k≤m, record the subset of retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the total number of points with the abscissa k, mark The point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax . N _kmax determination points corresponding to whether the line of sight L _kmax is blocked. If the line of sight L _kmax is blocked, set all the abscissas in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )} to k The line of sight corresponding to the point of is recorded as blocked. If the line of sight L _kmax is not blocked, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to establish a balanced binary search tree, and each of the balanced binary search trees The value of each node is the value of the ordinate of each point in the set. The nodes in the balanced binary search tree are traversed, and step four is executed.

步骤六：分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6: Take k=1, k=2,...,k=m respectively, repeat step 5 to complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.

进一步的，步骤(6)输出观山可视域数据并成像，生成观山可视域地图，具体方法如下：Further, step (6) output and image the viewable field data of the mountain to generate the viewable field map, the specific method is as follows:

(6.1)计算观山可视域数值(6.1) Calculate the value of the view field

对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1。定义一个MVF值，

MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率。 Line of sight _{L i ∈ {L 1, L} 2, ..., L s}, if L _i is flagged as being occluded, the given attribute value L _i μ _i = 0, L _i is marked as not blocked, then imparting L _{The i} attribute value μ _i =1. Define an MVF value,

The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints.

(6.2)通过颜色成像(6.2) Imaging by color

将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值。另外，设置渐变色条，如以绿色对应1完全看到，以白色代表0完全看不到，设置0-1之间不同数值对应不同的颜色，如从白色到绿色的渐变，根据MVF值的大小析出颜色，经过计算机计算，可对三维地图上多个观察区域进行以观山可视率为特征的颜色渲染，即根据MVF值设置观测点对应栅格的颜色，MVF值越大颜色越深，MVF值越小颜色越浅。Set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, and you can calculate the value of mountain visibility in real time. In addition, set the gradient color bar, such as green corresponding to 1 completely visible, white representing 0 completely invisible, setting different values between 0-1 to correspond to different colors, such as the gradient from white to green, according to the MVF value The size of the precipitation color, after computer calculation, the color rendering of multiple observation areas on the three-dimensional map can be characterized by the viewability of the mountain, which is to set the color of the grid corresponding to the observation point according to the MVF value. , The smaller the MVF value, the lighter the color.

(6.3)生成观山可视域地图(6.3) Generate a view of the mountain visual domain map

将富有MVF值颜色属性的观测区域模型重新置入整体的数据库场景，即将上述着色后的颜色栅格放进原来的模型对应的位置。The observation area model with rich MVF value color attributes is re-placed into the overall database scene, that is, the colored grid is placed in the position corresponding to the original model.

优选的，本专利可补充大气能见度约束。记某城市大气能见度数值为a，若某射线距离大于a，则该射线直接记为有物体遮挡。Preferably, this patent can supplement atmospheric visibility constraints. Record the atmospheric visibility value of a city as a. If the distance of a certain ray is greater than a, the ray is directly recorded as obscured by an object.

此外，本发明还提出一种城市观山可视域的测量***，该***包括如下模块：In addition, the present invention also provides a system for measuring the visual domain of urban mountain viewing, which includes the following modules:

整体场景建构模块，采集并建构包含山体及城市区域的实景三维模型场景；The overall scene construction module, which collects and constructs real 3D model scenes including mountains and urban areas;

观测区域全表面栅格化模块，提取观测区域，并对模型表面进行栅格化；The full surface rasterization module of the observation area extracts the observation area and rasterizes the model surface;

观察点球面坐标系创建模块，设定观察点并根据视野边界创建球体坐标系；Observation point spherical coordinate system creation module, set the observation point and create a spherical coordinate system according to the field of view boundary;

山体有效投影面切割模块，在球体坐标系中切割出山体有效投影面；Mountain effective projection surface cutting module, cut out the effective projection surface of the mountain in the spherical coordinate system;

观山视线遮挡计算模块，生成观山视线，并对视线是否被遮挡进行计算；The mountain sight occlusion calculation module generates the sight line of the mountain and calculates whether the sight line is blocked;

数据输出及成像模块，输出观山可视域数据并成像，生成观山可视域地图。The data output and imaging module outputs and images the viewable field data of the mountain to generate a map of the viewable field.

进一步的，所述整体场景建构模块的具体功能如下：Further, the specific functions of the overall scene construction module are as follows:

(1.1)通过实测获取包含山体及城市区域的倾斜摄影数据；(1.1) Obtain oblique photography data including mountains and urban areas through actual measurement;

(1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型；(1.2) According to the acquired oblique photographic data, a real 3D model based on real image texture is generated;

(1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型。(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform.

进一步的，所述观测区域全表面栅格化模块具体功能如下：Further, the specific functions of the full-surface rasterization module of the observation area are as follows:

(2.1)观测区域提取，在SuperMap平台加载倾斜摄影获得的实景三维模型中提取观测区域以观测山体；(2.1) Observation area extraction, extract the observation area from the real three-dimensional model obtained by loading oblique photography on the SuperMap platform to observe the mountain;

(2.2)对实景三维模型中的观测区域表面整体栅格化。(2.2) Rasterize the entire surface of the observation area in the real three-dimensional model.

进一步的，所述的观察点球面坐标系创建模块具体功能如下：Further, the specific functions of the observation point spherical coordinate system creation module are as follows:

(3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as a representative observation point of the grid;

(3.2)创建球体坐标系，将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点，其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度，以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径，作可视半球面，将该半球面定义为标准投影面P _s，以观察点Ο(x _o,y _o,z _o)为球心，分别以地理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

(3.2) create a sphere coordinate system, the urban space into viewer viewpoint three-dimensional space _{Ο (x o, y o,} z o), i.e. grid points observed, where, (x _o, y _o ) Is the coordinate value of the plane where the observer is, z _o is the height of the horizontal plane of the observation point, the horizontal plane V _h at the height of the observation point is the plane, and the maximum visible distance R _vmax in the current environment is the radius, which is the visible hemisphere , the hemispherical surface is defined as a standard projection plane P _s, to the viewpoint _{Ο (x o, y o,} z o) is the center of the sphere, respectively, the geographic coordinate system and perpendicular to the direction of true north direction is the horizontal vector V _h Base, establish a spherical coordinate system

(3.3)记该观察点的视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Record the angle values α _o and β _o between the field of view boundary of the observation point and the vector base in the north direction of the spherical coordinate system.

进一步的，所述的山体有效投影面切割模块的具体功能如下：Further, the specific functions of the effective projection surface cutting module of the mountain are as follows:

在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

其中同时r _t为该点到观察点的距离，

该点与观察点连线与正北方方向坐标轴的夹角，取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))，若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面，在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea，对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

Where r _t is the distance from the point to the observation point,

The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction is taken as the angular bisector of the viewing boundary of the observation point on the horizontal plane V _h . The angular bisector intersects the standard projection plane P _s at the point (R _vmax , 0,0.5(α _o +β _o )), if r _t ≥R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) will be the plane P _a tangent to the standard projection plane P _s , Then P _a is the approximate projection plane; if r _t <R _vmax , take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is the approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min (R _vmax ,r _t ),0,β _o ) is a straight line perpendicular to the horizontal plane V _h , then the approximate projection plane P _a is cut by the two straight lines as the approximate effective projection area P _ea , which is 2/3 of the height of the mountain The above area is taken as its projection on the approximate effective projection area _Pea , which is an approximate effective hill projection.

进一步的，所述的观山视线遮挡计算模块的具体功能如下：Further, the specific functions of the mountain view occlusion calculation module are as follows:

(5.1)生成观山视线，将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}，其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量，观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1； (5.1) Generate the view of the mountain, rasterize the effective mountain projection into m×n rectangular grid areas, take the grid center point in the lower left corner as the origin, and establish an orthogonal coordinate system on the approximate effective projection area P _ea ζ, the effective hill projection after rasterization is simplified to a point set composed of the center points of these grids {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s ( x _s ,y _s )}, where (x ₁ ,y ₁ ),(x ₂ ,y ₂ ),...,(x _s ,y _s ) are the points after the hill projection rasterized into a point set in two dimensions Discrete coordinates on the orthogonal coordinate system ζ, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid, observation point Ο to point N ₁ ,N The connection of ₂ ,...,N _s is denoted as the line of sight L ₁ ,L ₂ ,...,L _s . The center point of each grid has a weight w _i , where 0≤w _i ≤1;

(5.2)视线遮挡计算(5.2) Sight occlusion calculation

步骤一，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； Step ₁ : Search for the point with the abscissa of 0 in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, record The subset of the retrieved points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the abscissa is 0 The point with the largest ordinate is N _0max , and y _0max is the value of N _0max ordinate;

步骤二，判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； Step two, N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., In N _s (x _s ,y _s )}, the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

步骤三，以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Step 3: Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point in the set;

步骤四，每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Step 4: When traversing a node, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从 列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历；In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked;

步骤五，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值，判断点N _kmax对应的视线L _kmax是否被遮挡，若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡；若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四； Step 5: Retrieve the point with the abscissa of k in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, where , 0<k≤m, record the subset of the retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the point of the abscissa k In total, the point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax ordinate. It is judged whether the line of sight L _kmax corresponding to the point N _kmax is blocked. If the line of sight L _kmax is blocked, the point set {N ₁ ( x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )), the line of sight corresponding to all points with the abscissa k is recorded as occluded; if the line of sight L _{kmax is} not If it is occluded, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to build a balanced binary search tree, and the value of each node in the balanced binary search tree Is the value of the ordinate of each point in the set, traverse the nodes in the balanced binary search tree, and perform step four;

步骤六，分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6, respectively take k=1, k=2,...,k=m, repeat step 5, complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.

进一步的，所述数据输出及成像模块的具体功能如下：Further, the specific functions of the data output and imaging module are as follows:

(6.1)计算观山可视域数值，对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1，定义一个MVF值，

MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率； (6.1) Calculate the value of the viewable field of the mountain. For the line of sight L _i ∈ {L ₁ ,L ₂ ,...,L _s }, if _Li is marked as occluded, the attribute value of L _i is assigned μ _i = 0, L _i is marked as not blocked, the attribute value imparting L _i μ _i = 1, define a value MVF,

The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints;

(6.2)通过颜色成像，将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值，根据MVF值的大小设置观测点对应栅格的颜色；(6.2) Through color imaging, set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, you can calculate the value of mountain visibility in real time, and set the observation according to the MVF value The point corresponds to the color of the grid;

(6.3)生成观山可视域地图，即将上述着色后的颜色栅格放进原模型中对应的位置。(6.3) Generate a view of the mountain visual domain map, that is, put the colored grid into the corresponding position in the original model.

Claims (14)

1. 一种城市观山可视域的测量方法，其特征在于，该方法包括以下步骤：A method for measuring the visual field of urban mountain viewing, characterized in that the method includes the following steps:

   (1)采集并建构包含山体及城市区域的实景三维模型场景；(1) Collect and construct real-life 3D model scenes including mountains and urban areas;

   (2)提取观测区域，并对模型表面进行栅格化；(2) Extract the observation area and rasterize the model surface;

   (3)设定观察点并根据视野边界创建球体坐标系；(3) Set the observation point and create a spherical coordinate system according to the boundary of the field of view;

   (4)在球体坐标系中切割出山体有效投影面；(4) Cut out the effective projection surface of the mountain in the spherical coordinate system;

   (5)生成观山视线，并对视线是否被遮挡进行计算；(5) Generate the sight of the mountain and calculate whether the sight is blocked;

   (6)输出观山可视域数据并成像，生成观山可视域地图。(6) Output and image the visual field data of mountain viewing to generate a map of the visual field of mountain viewing.
2. 根据权利要求1所述的一种城市观山可视域的测量方法，其特征在于，步骤(1)中，采集并建构包含山体及城市区域的实景三维模型场景的方法如下：The method for measuring the visual domain of urban mountain viewing according to claim 1, wherein in step (1), the method of collecting and constructing a real three-dimensional model scene including the mountain and the urban area is as follows:

   (1.1)通过实测获取包含山体及城市区域的倾斜摄影数据；(1.1) Obtain oblique photography data including mountains and urban areas through actual measurement;

   (1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型；(1.2) According to the acquired oblique photographic data, a real 3D model based on real image texture is generated;

   (1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型。(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform.
3. 根据权利要求1或2所述的一种城市观山可视域的高精度测度方法，其特征在于，步骤(2)中，提取观测区域，并对模型表面进行栅格化的方法如下：A high-precision measurement method of the visual domain of urban mountain viewing according to claim 1 or 2, characterized in that, in step (2), the method of extracting the observation area and rasterizing the model surface is as follows:

   (2.1)在实景三维模型中提取观测区域；(2.1) Extract the observation area from the real 3D model;

   (2.2)对实景三维模型中的观测区域表面整体栅格化。(2.2) Rasterize the entire surface of the observation area in the real three-dimensional model.
4. 根据权利要求3所述的一种城市观山可视域的测量方法，其特征在于，步骤(3)中，设定观察点并根据视线夹角创建球体坐标系的方法如下：The method for measuring the visual domain of urban mountain viewing according to claim 3, wherein in step (3), the method of setting the observation point and creating a spherical coordinate system according to the angle of sight is as follows:

   (3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格的观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as the observation point representing the grid;

   (3.2)创建球体坐标系，将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点，其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度，以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径，作可视半球面，将该半球面定义为标准投影面P _s，以观察点Ο(x _o,y _o,z _o)为球心，分别以地理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

   

   (3.2) create a sphere coordinate system, the urban space into viewer viewpoint three-dimensional space _{Ο (x o, y o,} z o), i.e. grid points observed, where, (x _o, y _o ) Is the coordinate value of the plane where the observer is, z _o is the height of the horizontal plane of the observation point, the horizontal plane V _h at the height of the observation point is the plane, and the maximum visible distance R _vmax in the current environment is the radius, which is the visible hemisphere , the hemispherical surface is defined as a standard projection plane P _s, to the viewpoint _{Ο (x o, y o,} z o) is the center of the sphere, respectively, the geographic coordinate system and perpendicular to the direction of true north direction is the horizontal vector V _h Base, establish a spherical coordinate system

   

   (3.3)记该观察点的视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Record the angle values α _o and β _o between the field of view boundary of the observation point and the vector base in the north direction of the spherical coordinate system.
5. 根据权利要求4所述的一种城市观山可视域的测量方法，其特征在于，步骤(4)中，在球体坐标系中切割出山体有效投影面方法如下：The method for measuring the visual domain of urban mountain viewing according to claim 4, wherein, in step (4), the method of cutting out the effective projection surface of the mountain in the spherical coordinate system is as follows:

   在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

   

   其中同时r _t为该点到观察点的距离，

   

   该点与观察点连线与正北方方向坐标轴的夹角，取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))，若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

   

   作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面，在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea，对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

   

   Where r _t is the distance from the point to the observation point,

   

   The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction is taken as the angular bisector of the viewing boundary of the observation point on the horizontal plane V _h . The angular bisector intersects the standard projection plane P _s at the point (R _vmax , 0,0.5(α _o +β _o )), if r _t ≥R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) will be the plane P _a tangent to the standard projection plane P _s , Then P _a is the approximate projection plane; if r _t <R _vmax , take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

   

   Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is the approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min (R _vmax ,r _t ),0,β _o ) is a straight line perpendicular to the horizontal plane V _h , then the approximate projection plane P _a is cut by the two straight lines as the approximate effective projection area P _ea , which is 2/3 of the height of the mountain The above area is taken as its projection on the approximate effective projection area _Pea , which is an approximate effective hill projection.
6. 根据权利要求5所述的一种城市观山可视域的高精度测度方法，其特征在于，步骤 (5)生成观山视线，并对视线是否被遮挡进行计算，具体方法如下：A high-precision measurement method for the visual domain of urban mountain viewing according to claim 5, wherein step (5) generates the mountain viewing line of sight, and calculates whether the line of sight is blocked, the specific method is as follows:

   (5.1)生成观山视线，将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}，其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量，观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1； (5.1) Generate the view of the mountain, rasterize the effective mountain projection into m×n rectangular grid areas, take the grid center point in the lower left corner as the origin, and establish an orthogonal coordinate system on the approximate effective projection area P _ea ζ, the effective hill projection after rasterization is simplified to a point set composed of the center points of these grids {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s ( x _s ,y _s )}, where (x ₁ ,y ₁ ),(x ₂ ,y ₂ ),...,(x _s ,y _s ) are the points after the hill projection rasterized into a point set in two dimensions Discrete coordinates on the orthogonal coordinate system ζ, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid, observation point Ο to point N ₁ ,N The connection of ₂ ,...,N _s is denoted as the line of sight L ₁ ,L ₂ ,...,L _s . The center point of each grid has a weight w _i , where 0≤w _i ≤1;

   (5.2)视线遮挡计算(5.2) Sight occlusion calculation

   步骤一，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； Step ₁ : Search for the point with the abscissa of 0 in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, record The subset of the retrieved points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the abscissa is 0 The point with the largest ordinate is N _0max , and y _0max is the value of N _0max ordinate;

   步骤二，判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； Step two, N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., In N _s (x _s ,y _s )}, the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

   步骤三，以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Step 3: Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point in the set;

   步骤四，每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Step 4: When traversing a node, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

   若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

   若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

   若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

   若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

   在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历；In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked;

   步骤五，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值，判断点N _kmax对应的视线L _kmax是否被遮挡，若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡；若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四； Step 5: Retrieve the point with the abscissa of k in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, where , 0<k≤m, record the subset of the retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the point of the abscissa k In total, the point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax ordinate. It is judged whether the line of sight L _kmax corresponding to the point N _kmax is blocked. If the line of sight L _kmax is blocked, the point set {N ₁ ( x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )), the line of sight corresponding to all points with the abscissa k is recorded as occluded; if the line of sight L _{kmax is} not If it is occluded, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to build a balanced binary search tree, and the value of each node in the balanced binary search tree Is the value of the ordinate of each point in the set, traverse the nodes in the balanced binary search tree, and perform step four;

   步骤六，分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6, respectively take k=1, k=2,...,k=m, repeat step 5, complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.
7. 根据权利要求6所述的一种城市观山可视域的测量方法，其特征在于，步骤(6)输出 观山可视域数据并成像，生成观山可视域地图，具体方法如下：The method for measuring the visual area of urban mountain viewing according to claim 6, wherein step (6) outputs and images the visual field of mountain viewing data to generate a map of the visual field of mountain viewing. The specific method is as follows:

   (6.1)计算观山可视域数值，对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1，定义一个MVF值，

   

   MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率； (6.1) Calculate the value of the viewable field of the mountain. For the line of sight L _i ∈ {L ₁ ,L ₂ ,...,L _s }, if _Li is marked as occluded, the attribute value of L _i is assigned μ _i = 0, L _i is marked as not blocked, the attribute value imparting L _i μ _i = 1, define a value MVF,

   

   The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints;

   (6.2)通过颜色成像，将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值，根据MVF值的大小设置观测点对应栅格的颜色；(6.2) Through color imaging, set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, you can calculate the value of mountain visibility in real time, and set the observation according to the MVF value The point corresponds to the color of the grid;

   (6.3)生成观山可视域地图，即将上述着色后的颜色栅格放进原模型中对应的位置。(6.3) Generate a view of the mountain visual domain map, that is, put the colored grid into the corresponding position in the original model.
8. 一种城市观山可视域的测量***，其特征在于，该***包括如下模块：A measurement system for urban mountain viewing visual domain, which is characterized in that the system includes the following modules:

   整体场景建构模块，采集并建构包含山体及城市区域的实景三维模型场景；The overall scene construction module, which collects and constructs real 3D model scenes including mountains and urban areas;

   观测区域全表面栅格化模块，提取观测区域，并对模型表面进行栅格化；The full surface rasterization module of the observation area extracts the observation area and rasterizes the model surface;

   观察点球面坐标系创建模块，设定观察点并根据视野边界创建球体坐标系；Observation point spherical coordinate system creation module, set the observation point and create a spherical coordinate system according to the field of view boundary;

   山体有效投影面切割模块，在球体坐标系中切割出山体有效投影面；Mountain effective projection surface cutting module, cut out the effective projection surface of the mountain in the spherical coordinate system;

   观山视线遮挡计算模块，生成观山视线，并对视线是否被遮挡进行计算；The mountain sight occlusion calculation module generates the sight line of the mountain and calculates whether the sight line is blocked;

   数据输出及成像模块，输出观山可视域数据并成像，生成观山可视域地图。The data output and imaging module outputs and images the viewable field data of the mountain to generate a map of the viewable field.
9. 根据权利要求8所述的一种城市观山可视域的测量***，其特征在于，整体场景建构模块的具体功能如下：The measurement system for the visual domain of urban mountain viewing according to claim 8, wherein the specific functions of the overall scene building module are as follows:

   (1.1)通过实测获取包含山体及城市区域的倾斜摄影数据；(1.1) Obtain oblique photography data including mountains and urban areas through actual measurement;

   (1.2)根据获取的倾斜摄影数据生成基于真实影像纹理的实景三维模型；(1.2) According to the acquired oblique photographic data, a real 3D model based on real image texture is generated;

   (1.3)通过SuperMap平台加载根据倾斜摄影数据获得的实景三维模型。(1.3) Load the real 3D model obtained from the oblique photography data through the SuperMap platform.
10. 根据权利要求8或9所述的一种城市观山可视域的测量***，其特征在于，观测区域全表面栅格化模块具体功能如下：The measurement system for the visual area of urban mountain viewing according to claim 8 or 9, wherein the specific functions of the full surface rasterization module of the observation area are as follows:

    (2.1)在实景三维模型中提取观测区域；(2.1) Extract the observation area from the real 3D model;

    (2.2)对实景三维模型中的观测区域表面整体栅格化。(2.2) Rasterize the entire surface of the observation area in the real three-dimensional model.
11. 根据权利要求10所述的一种城市观山可视域的测量***，其特征在于，观察点球面坐标系创建模块具体功能如下：The measurement system for urban mountain viewing visual domain according to claim 10, wherein the specific functions of the observation point spherical coordinate system creation module are as follows:

    (3.1)设定观察点坐标，选取每个栅格的几何中心点，作为代表该栅格观察点；(3.1) Set the coordinates of the observation point, and select the geometric center point of each grid as a representative observation point of the grid;

    (3.2)创建球体坐标系，将城市空间中的观察者转化为三维空间中的观察点Ο(x _o,y _o,z _o)，也即栅格观察点，其中，(x _o,y _o)为观察者所在的平面坐标值，z _o为观察点的水平面高度，以观察点所在高度的水平面V _h为平面，以当前环境下的最大可视距离R _vmax为半径，作可视半球面，将该半球面定义为标准投影面P _s，以观察点Ο(x _o,y _o,z _o)为球心，分别以地理坐标系中的正北方向和水平面V _h的垂直方向为矢基，建立球体坐标系

    

    (3.2) create a sphere coordinate system, the urban space into viewer viewpoint three-dimensional space _{Ο (x o, y o,} z o), i.e. grid points observed, where, (x _o, y _o ) Is the coordinate value of the plane where the observer is, z _o is the height of the horizontal plane of the observation point, the horizontal plane V _h at the height of the observation point is the plane, and the maximum visible distance R _vmax in the current environment is the radius, which is the visible hemisphere , the hemispherical surface is defined as a standard projection plane P _s, to the viewpoint _{Ο (x o, y o,} z o) is the center of the sphere, respectively, the geographic coordinate system and perpendicular to the direction of true north direction is the horizontal vector V _h Base, establish a spherical coordinate system

    

    (3.3)记该观察点的视野边界与球体坐标系正北方向矢基的夹角值α _o和β _o。 (3.3) Record the angle values α _o and β _o between the field of view boundary of the observation point and the vector base in the north direction of the spherical coordinate system.
12. 根据权利要求11所述的一种城市观山可视域的测量***，其特征在于，山体有效投影面切割模块的具体功能如下：The measurement system for the visual domain of urban mountain viewing according to claim 11, wherein the specific functions of the mountain effective projection surface cutting module are as follows:

    在球面坐标系中作山体在水平面V _h上的投影P _h，取投影P _h中与观察点距离最大的点，记该点坐标为

    

    其中同时r _t为该点到观察点的距离，

    

    该点与观察点连线与正北方 方向坐标轴的夹角，取观察点在水平面V _h上的视野边界的角平分线，该角平分线与标准投影面P _s相交于点(R _vmax,0,0.5(α _o+β _o))，若r _t≥R _vmax，则过点(R _vmax,0,0.5(α _o+β _o))作与标准投影面P _s相切的平面P _a，则P _a为近似投影平面；若r _t<R _vmax，则以观察点所在高度的水平面V _h为平面，以r _t为半径，作参考半球面C _v，然后过点

    

    作与参考半球面C _v相切的平面P _a，则P _a为近似投影平面，在近似投影平面P _a上，分别过(min(R _vmax,r _t),0,α _o)和(min(R _vmax,r _t),0,β _o)作垂直于水平面V _h的直线，则近似投影平面P _a被两条直线切割出的区域为近似有效投影区域P _ea，对山体高度2/3以上区域，作其在近似有效投影区域P _ea上的投影，该投影为近似有效山体投影。 In the spherical coordinate system, make the projection P _{h of the} mountain on the horizontal plane V _h , take the point with the largest distance from the observation point in the projection P _h , and record the coordinate of this point as

    

    Where r _t is the distance from the point to the observation point,

    

    The angle between the line connecting this point and the observation point and the coordinate axis in the true north direction is taken as the angular bisector of the viewing boundary of the observation point on the horizontal plane V _h . The angular bisector intersects the standard projection plane P _s at the point (R _vmax , 0,0.5(α _o +β _o )), if r _t ≥R _vmax , then the crossing point (R _vmax ,0,0.5(α _o +β _o )) will be the plane P _a tangent to the standard projection plane P _s , Then P _a is the approximate projection plane; if r _t <R _vmax , take the horizontal plane V _h at the height of the observation point as the plane, and take r _t as the radius, as the reference hemisphere C _v , and then pass the point

    

    Draw a plane P _a tangent to the reference hemisphere C _v , then P _a is the approximate projection plane. On the approximate projection plane P _a , pass (min(R _vmax ,r _t ),0,α _o ) and (min (R _vmax ,r _t ),0,β _o ) is a straight line perpendicular to the horizontal plane V _h , then the approximate projection plane P _a is cut by the two straight lines as the approximate effective projection area P _ea , which is 2/3 of the height of the mountain The above area is taken as its projection on the approximate effective projection area _Pea , which is an approximate effective hill projection.
13. 根据权利要求12所述的一种城市观山可视域的测量***，其特征在于，观山视线遮挡计算模块的具体功能如下：The system for measuring the visual area of urban mountain viewing according to claim 12, wherein the specific functions of the mountain viewing occlusion calculation module are as follows:

    (5.1)生成观山视线，将有效山体投影栅格化在m×n个矩形栅格区域中，以左下角的栅格中心点为原点，在近似有效投影区域P _ea上建立正交坐标系ζ，将栅格化后的有效山体投影简化为由这些栅格的中心点构成的点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}，其中，(x ₁,y ₁),(x ₂,y ₂),…,(x _s,y _s)为山体投影栅格化为点集后的点在二维正交坐标系ζ上的离散坐标，0≤x _i≤m,0≤y _i≤n，1<i<S，S为栅格的中心点的总数量，观察点Ο到点N ₁,N ₂,…,N _s的连线，记为视线L ₁,L ₂,…,L _s，每个栅格的中心点拥有权重w _i，其中，0≤w _i≤1； (5.1) Generate the view of the mountain, rasterize the effective mountain projection into m×n rectangular grid areas, take the grid center point in the lower left corner as the origin, and establish an orthogonal coordinate system on the approximate effective projection area P _ea ζ, the effective hill projection after rasterization is simplified to a point set composed of the center points of these grids {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s ( x _s ,y _s )}, where (x ₁ ,y ₁ ),(x ₂ ,y ₂ ),...,(x _s ,y _s ) are the points after the hill projection rasterized into a point set in two dimensions Discrete coordinates on the orthogonal coordinate system ζ, 0≤x _i ≤m, 0≤y _i ≤n, 1<i<S, S is the total number of center points of the grid, observation point Ο to point N ₁ ,N The connection of ₂ ,...,N _s is denoted as the line of sight L ₁ ,L ₂ ,...,L _s . The center point of each grid has a weight w _i , where 0≤w _i ≤1;

    (5.2)视线遮挡计算(5.2) Sight occlusion calculation

    步骤一，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为0的点进行检索，记检索出的点构成的子集为{N ₁(0,y ₁),…,N _j(0,y _0max)}，其中，j为横坐标为0的点的总数，记横坐标为0的纵坐标最大的点为N _0max，y _0max为N _0max纵坐标的值； Step ₁ : Search for the point with the abscissa of 0 in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, record The subset of the retrieved points is {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, where j is the total number of points with an abscissa of 0, and the abscissa is 0 The point with the largest ordinate is N _0max , and y _0max is the value of N _0max ordinate;

    步骤二，判断点N _0max对应的视线L _0max否被遮挡，若视线L _0max被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为0的点对应的视线记为被遮挡；若视线L _0max未被遮挡，则执行步骤三； Step two, N _0max determination points corresponding to the line of sight is blocked L _0max NO, if the line of sight L _0max is blocked, then the point set _{{N 1 (x 1, y} 1), N 2 (x 2, y 2), ..., In N _s (x _s ,y _s )}, the line of sight corresponding to all the points with the abscissa of 0 is recorded as blocked; if the line of sight L _0max is not blocked, go to step 3;

    步骤三，以集合{N ₁(0,y ₁),…,N _j(0,y _0max)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历； Step 3: Set up a balanced binary search tree with the points in the set {N ₁ (0,y ₁ ),...,N _j (0,y _0max )}, and the value of each node in the balanced binary search tree Traverse the nodes in the balanced binary search tree with the value of the ordinate of each point in the set;

    步骤四，每遍历一个结点，计算该结点对应的视线是否被遮挡，并将该结点对应的视线是否被遮挡这一属性记录在一个列表中；Step 4: When traversing a node, calculate whether the line of sight corresponding to the node is occluded, and record the attribute of whether the line of sight corresponding to the node is occluded in a list;

    若该结点对应的视线未被遮挡，则继续遍历其左子树，并将该结点和该结点的右子树上的全部点对应的视线定义为未被遮挡；If the line of sight corresponding to the node is not blocked, continue to traverse the left subtree, and define the line of sight corresponding to all points on the node and the right subtree of the node as unblocked;

    若该结点对应的视线已被遮挡，则将该结点和该结点的左子树上的全部点对应的视线定义为已被遮挡，并计算该结点的右子结点对应的视线是否被遮挡：If the line of sight corresponding to the node has been occluded, the line of sight corresponding to the node and all points on the left subtree of the node is defined as occluded, and the line of sight corresponding to the right sub-node of the node is calculated Is it blocked:

    若该结点的右子结点对应的视线未被遮挡，则将其余未被标记的结点对应的视线定义为未被遮挡，并停止遍历；If the line of sight corresponding to the right child node of the node is not blocked, the line of sight corresponding to the remaining unmarked nodes is defined as unblocked, and the traversal is stopped;

    若该结点的右子结点对应的视线已被遮挡，则继续遍历其右子树；If the line of sight corresponding to the right child node of the node has been blocked, continue to traverse the right child tree;

    在遍历结点的过程中，若遇到已标记过对应的视线是否被遮挡的结点，则直接从列表中读取它对应的视线是否被遮挡的结果，当所有结点对应的视线是否被遮挡都以被标记时，停止遍历；In the process of traversing the nodes, if you encounter a node that has been marked whether the corresponding line of sight is blocked, read the result of whether its corresponding line of sight is blocked directly from the list, and when all the nodes correspond to whether the line of sight is blocked Stop traversing when all the occlusions are marked;

    步骤五，对于点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中横坐标为k的点进行检索，其 中，0<k≤m，记检索出的点构成的子集为{N ₁(k,y ₁),…,N _j(k,y _kmax)}，其中，j为横坐标为k的点的总数，记纵坐标最大的点为N _kmax，y _kmax为N _kmax纵坐标的值，判断点N _kmax对应的视线L _kmax是否被遮挡，若视线L _kmax被遮挡，则将点集{N ₁(x ₁,y ₁),N ₂(x ₂,y ₂),…,N _s(x _s,y _s)}中所有横坐标为k的点对应的视线记为被遮挡；若视线L _kmax未被遮挡，则以集合{N ₁(k,y ₁),…,N _j(k,y _kmax)}中的点建立平衡二叉搜索树，平衡二叉搜索树的中每个结点的值为集合中每个点的纵坐标的值，对该平衡二叉搜索树中的结点进行遍历，执行步骤四； Step 5: Retrieve the point with the abscissa of k in the point set {N ₁ (x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),...,N _s (x _s ,y _s )}, where , 0<k≤m, record the subset of the retrieved points as {N ₁ (k,y ₁ ),...,N _j (k,y _kmax )}, where j is the point of the abscissa k In total, the point with the largest ordinate is N _kmax , and y _kmax is the value of N _kmax ordinate. It is judged whether the line of sight L _kmax corresponding to the point N _kmax is blocked. If the line of sight L _kmax is blocked, the point set {N ₁ ( x ₁ ,y ₁ ),N ₂ (x ₂ ,y ₂ ),…,N _s (x _s ,y _s )), the line of sight corresponding to all points with the abscissa k is recorded as occluded; if the line of sight L _{kmax is} not If it is occluded, the points in the set {N ₁ (k,y ₁ ),…,N _j (k,y _kmax )} are used to build a balanced binary search tree, and the value of each node in the balanced binary search tree Is the value of the ordinate of each point in the set, traverse the nodes in the balanced binary search tree, and perform step four;

    步骤六，分别取k＝1,k＝2,…,k＝m,重复步骤五，完成全部视线L ₁,L ₂,…,L _s是否被遮挡的计算。 Step 6, respectively take k=1, k=2,...,k=m, repeat step 5, complete the calculation of whether all the sight lines L ₁ , L ₂ ,..., L _s are blocked.
14. 根据权利要求13所述的一种城市观山可视域的测量***，其特征在于，数据输出及成像模块的具体功能如下：The measurement system for the visual domain of urban mountain viewing according to claim 13, wherein the specific functions of the data output and imaging module are as follows:

    (6.1)计算观山可视域数值，对于视线L _i∈{L ₁,L ₂,…,L _s}，若L _i被标记为被遮挡，则赋予L _i属性值μ _i＝0，L _i被标记为未被遮挡，则赋予L _i属性值μ _i＝1，定义一个MVF值，

    

    MVF的取值范围为[0,1]，它代表观察者在一定大气能见度约束下，在某一观察点的观山可视率； (6.1) Calculate the value of the viewable field of the mountain. For the line of sight L _i ∈ {L ₁ ,L ₂ ,...,L _s }, if _Li is marked as occluded, the attribute value of L _i is assigned μ _i = 0, L _i is marked as not blocked, the attribute value imparting L _i μ _i = 1, define a value MVF,

    

    The value range of MVF is [0,1], which represents the viewability of the observer at a certain observation point under certain atmospheric visibility constraints;

    (6.2)通过颜色成像，将三维地图上的一点设置为观察点，输入最大可视距离和观察观察者的视野角度范围，可以实时计算观山可视率的值，根据MVF值的大小设置观测点对应栅格的颜色；(6.2) Through color imaging, set a point on the three-dimensional map as an observation point, enter the maximum visible distance and the observer's field of view angle range, you can calculate the value of mountain visibility in real time, and set the observation according to the MVF value The point corresponds to the color of the grid;

    (6.3)生成观山可视域地图，即将上述着色后的颜色栅格放进原模型中对应的位置。(6.3) Generate a view of the mountain visual domain map, that is, put the colored grid into the corresponding position in the original model.

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