CN105550639A - Automatic extraction method for Earth observation laser height measurement satellite elevation control points and data processing method - Google Patents

Abstract

The invention relates to an automatic extraction method for Earth observation laser height measurement satellite elevation control points and a data processing method. The laser elevation control point extraction method comprises steps that an effective earth observation laser distance value measurement evaluation method is employed, determined cloudless footprint image blocks are kept, and laser elevation data of determined thin-cloud or thick-cloud footprint image blocks are removed; reflectivity Epsilon smaller than 1 of laser footprint points is taken as a screening parameter, laser footprint points of the kept footprint image blocks are screened, Epsilon=reception pulse energy/emission pulse energy, laser footprint points which have only one wave peak, have the peak value greater than the threshold, have the standard deviation sigma not greater than 3.2ns after waveform fitting are selected from an echo waveform, and parameters used for determining the threshold comprise the emission energy and a reception caliber of a laser device. Through the method, influence of clouds on laser distance measurement can be reduced, laser distance measurement precision can be guaranteed, and accuracy of the laser elevation reference data is effectively improved.

Description

Earth observation laser-measured height satellite elevation reference mark extraction method and data processing method

Technical field

The present invention relates to satellite data disposal route, more specifically relate to a kind of cloud and mist quantity measuring method of laser footmark image and the vertical control point extraction method detected based on echo waveform process and cloud and mist amount and earth observation laser-measured height satellite data disposal route.

Background technology

Along with expanding economy, three-dimensional geographic information is used widely in each side such as digital earth, city planning, environmental protection.And the fast development of remote sensing satellite technology, space photogrammetry is made to have become the means of another quick obtaining three-dimensional geographic information after photogrammetric measurement, particularly in recent years along with the development of the technology such as three line scanner stereoscopic camera, the acquiring technology of 3 D Remote Sensing information achieves significant progress.

Such as, No. three, resource is the civilian stereoplotting satellite of China's first high precision, and succeeding in sending up and effectively applying of it has broken China for a long time to the dependence of external high precision satellite image, creates huge Social and economic [email protected] due to aspects such as optical stereo satellite stereoplotting mode and Satellite Attitude rail measuring accuracy, camera distortions, cause it under the condition of Pillarless caving, its measurement of higher degree precision is also difficult to the demand meeting high precision mapping.

Ground control point GCP (GroundControlPoints) be satellite remote sensing image geometry correct and geo-location time important reference data sources.Correct in processing procedure at remotely sensing image geometric, for reaching certain correction precision, the ground control point of some is absolutely necessary, build video imaging model by the object coordinates at reference mark and corresponding picpointed coordinate and solving model parameter or compensation is optimized to existing imaging model solves compensating parameter, finally set up the correct transformational relation of object space and image space in imaging process.

Reference mark in traditional work process generally adopts the pattern of full field survey, need the operation through series of complexes such as " collect existing control data, survey that district is made an on-the-spot survey, reconnaissance is laying of markstone, field operation is measured, the arrangement of interior industry ", although along with the development of the advanced measuring techniques such as GPS-RTK, the workload that field operation is measured and complexity greatly reduce, but the reference mark field survey work of necessity is still inevitable.

In addition, because satellite remote-sensing image coverage is large (for resource No. three satellites, coverage is 50 kilometers × 50 kilometers), want to obtain equally distributed ground control point, the testing in the scope of hundreds of kilometer and even thousands of square kilometres of usual needs, its field process amount is big, labor intensive and material resources are self-evident.In addition, in the uninhabited areas such as disaster hotspots or virgin forest, marsh, desert such as earthquake, flood, rubble flow, survey crew usually cannot enter and measure on the spot.

Even if reference mark being by manually choosing remote sensing image and topomap same place obtains, also there is inefficiency, precision is difficult to the problems such as guarantee.And the different phase of areal or different sensors image are corrected, there will be again the situation of repetition reconnaissance.

Ground control point is generally divided into: flat high reference mark, planimetric control point and vertical control point.Chinese patent application 201310143369.3 discloses a kind of multi-source heterogeneous remote sensing image reference mark automatic acquiring method, can automatically extract remote sensing from multi-source heterogeneous image and control imaging point (reference mark image film), improve efficiency and the precision of control data acquisition, but it is in fact still a kind of automatic acquiring method of planimetric control point.

When ground control point data deficiencies, the area adjustment technology of satellite image can as a kind of important means of precise geometrical location.Such as, Chinese invention patent application 201510191096.9 discloses a kind of satellite image stereoblock adjustment method based on spaceborne laser altimeter system data.In the scheme disclosed in this patented claim, adopt spaceborne laser altimeter system data as the control data of broad sense vertical control point database.

Carrying out whole world mapping, is for necessity of protection China territorial sovereignty, relevant benefit and geography information safety supports.Satellite remote sensing technology has unique advantage obtaining in overseas geography information.At present, mapping geography information office of country just around the Major Strategic Demand such as " band one tunnel ", " high ferro is walked out ", progressively carries out global High Precision Stereo mapping.And carry out measurement and the acquisition of global vertical control point, be then the important technology guarantee carrying out whole world mapping.Therefore, for carrying out the relevant work of global mapping smoothly, preferentially must carry out the acquisition of global high-precision control point, setting up corresponding reference mark database.Utilizing laser-measured height satellite to carry out global vertical control point acquisition, is under current satellite remote sensing technology condition, a kind of effective technological means.

Spaceborne laser altimeter system is a kind of ground point High head ratio technology, it take satellite as platform, carry laser ceilometer from space, the time observes the earth, high precision, measure distance between satellite to testee in real time, and by data process&analysis, obtain the information such as landforms, vegetative coverage situation, ocean surface topography of earth surface.External spaceborne laser altimeter system technical development is rapid, and world's Main Developed Countries is all in the research carrying out spaceborne laser altimeter system instrument.Such as, the U.S. transmitted ICESat satellite in 2003, the geoscience laser-measured height instrument system (GeoscienceLaserAltimeterSystem that it carries, GLAS) be first the satellite borne laser range measurement system for the Continuous Observation earth in the whole world, its main science object measures polar ice sheet elevation and change thereof, cloud layer and aerocolloidal distribution characteristics etc.ICESat satellite is period in orbit, and obtain a large amount of high-precision altitude figures, its laser footmark plane precision reaches 10m magnitude, and vertical accuracy is about 15cm.

Domestic attach great importance in recent years spaceborne laser altimeter system research.Moon exploration program series of satellites " Chang'e I " and " Chang'e-2 " satellite of independent research have all carried high-precision laser ceilometer, obtain moonscape 3 D stereoscopic image.Except " goddess in the moon " series of satellites carries except laser ceilometer, also not used for the laser-measured height system of earth observation, but list follow-up earth observation laser-measured height satellite development plan in, the civilian stereoplotting satellite of high precision as 1:1 ten thousand engineer's scale, terrestrial ecosystems carbon monitor satellite etc., all will carry the laser ceilometer of earth observation.

Earth observation laser-measured height satellite comes and goes in the process of air in laser beam, the phenomenon such as scattering, refraction can be produced with atmospheric molecule and gasoloid, and then cause laser energy to occur decay, echo distortion, degradation problem under distance accuracy, the particularly spissatus impact of its medium cloud is particularly remarkable, in order to ensure the precision of laser ranging, need to reduce cloud layer to the impact of laser ranging as far as possible, ensure that the laser ranging value obtained is effective.

Summary of the invention

According to an embodiment of the invention on the one hand, provide a kind of cloud and mist quantity measuring method of laser footmark image, it comprises: utilize a large amount of cloud and mist images that contains to carry out sample training, obtain preferred gray threshold and the textural characteristics value of cloud and mist; Calculate the grey level histogram of view picture footmark image, tentatively judge whether to there is cloud and mist based on described preferred gray threshold, and the content of cloud and mist; Calculate the gray average of the sub-block of footmark image, when the gray average of described sub-block is higher than judging containing cloud and mist during first threshold, when the gray average of described sub-block is lower than judging not containing cloud and mist during Second Threshold; Utilize gray level co-occurrence matrixes calculating gray average to be in the textural characteristics of the image sub-block between described first threshold and Second Threshold, contrast with the described cloud and mist textural characteristics value obtained from described sample training; Statistics is judged as the sum of all pixels of cloud and mist and the quantity accounting in described view picture footmark image thereof, determines cloud and mist amount.

According to the laser footmark image cloud and mist quantity measuring method of the embodiment of the present invention, alternatively, when calculating the grey level histogram of view picture footmark image, carry out histogram equalization to image and strengthen process, the formula of equalization is as follows:

$s_k=T\left(r_k\right)=\underset{i=0}{\overset{k}{\Σ}}{P}_r\left(r_i\right)=\underset{i=0}{\overset{k}{\Σ}}\frac{n_i}{n}$

0≤r _k≤1,k＝0,1,2,...L-1

Wherein, s _kfor the new gray-scale value of pixel after conversion that former figure gray-scale value is k; P _r(r _i) dot frequency of to be gray-scale value be i; L is the gray shade scale of image.

According to the laser footmark image cloud and mist quantity measuring method of the embodiment of the present invention, alternatively, during described first threshold 235, described Second Threshold is 80.

According to the laser footmark image cloud and mist quantity measuring method of the embodiment of the present invention, alternatively, the textural characteristics considered when utilizing gray level co-occurrence matrixes to calculate the textural characteristics of described image sub-block comprises: angle second moment, homogeney, one or more in contrast and correlativity.

According to an embodiment of the invention on the other hand, provide a kind of earth observation laser ranging value efficiency assessment method, it comprises: what pass down for laser-measured height satellite carries out system Geometric correction and preliminary waveform processing through decoded raw data, according to geometrical correspondence, obtain footmark image corresponding to laser facula, the preliminary demarcation based on hardware parameter and geographic coordinate or footmark camera and laser ceilometer realizes the basic registration of laser and footmark image; Determine the center position of the obtained footmark image corresponding with laser facula, and determine the area that in footmark image, laser facula is corresponding; The image determined is carried out cutting or stored in forming footmark image blocks in internal memory; Adopt aforesaid cloud and mist quantity measuring method, the detection of cloud and mist amount is carried out to described footmark image blocks, obtain the cloud and mist value of footmark image blocks; Validity or the availability of the laser ranging value of described footmark image blocks is judged based on described cloud and mist value.

Another according to an embodiment of the invention aspect, provide a kind of laser height Control point extraction method, it comprises: adopt aforesaid earth observation laser ranging value efficiency assessment method, retain and be judged to be cloudless footmark image blocks, weed out the laser height data being judged to be thin cloud or spissatus footmark image blocks; Using the reflectivity ε <1 of laser footmark point as screening parameter, screen the laser footmark point of the footmark image blocks of described reservation, wherein, select only there is a crest in echo waveform, peak value is greater than threshold value and the laser footmark point of standard deviation≤3.2ns after waveform fitting, wherein, for determining that the parameter of described threshold value comprises emitted energy and the Receiver aperture of laser instrument.

According to the laser height Control point extraction method of the embodiment of the present invention, alternatively, the mode adopting multiple Gaussian function to superpose carries out waveform fitting to described echo waveform, and fitting formula is shown below:

$w\left(t\right)=\mathrm{\&epsiv;}+\underset{m=1}{\overset{p}{\&Sigma;}}{A}_m{e}^{(-\frac{{(t-t_m)}^2}{2{{\mathrm{\&sigma;}}_m}^2})}$

In above formula, t is the time, A _m, t _m, σ _mbe respectively the amplitude of m Gaussian function, average and standard deviation, ε is wave noise value.

According to an embodiment of the invention more on the one hand, provide a kind of earth observation laser-measured height satellite data disposal route, it comprises:, denoising smoothing to the transmitting and receiving waveform of laser, extract waveform feature parameter, determine to transmit and receive moment corresponding to waveform center of gravity, according to the Laser Transmission time interval, calculate laser one-way transmission initial distance value; According to Satellite Attitude rail parameter, laser emission time, initial distance value and laser geometric location model, calculate the rough three-dimensional coordinate of laser footmark point; According to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, footmark image geometric rough correct product is produced in resampling; Adopt aforesaid cloud and mist quantity measuring method, carry out the detection of cloud and mist amount to footmark image, the laser footmark point cloud and mist value detected not being exceeded to the footmark image of preassigned is for further processing.

According to the earth observation laser-measured height satellite data disposal route of the embodiment of the present invention, alternatively, also comprise: adopt atmospheric delay correction model, obtain atmospheric delay correction value according to atmospheric parameter and the rough three-dimensional coordinate of described laser footmark point; According to laser distance measuring system error amount, described initial distance value, described atmospheric delay correction value that geometry calibration obtains, calculate accurate distance value; According to Satellite Attitude rail parameter, laser emission time, described accurate distance value and laser geometric location model, calculate laser footmark point three-dimensional coordinate; Adopt tide correction model, calculate tidal difference, described calculating laser footmark point three-dimensional coordinate is revised, obtain laser footmark point accurate three-dimensional coordinate.

According to the earth observation laser-measured height satellite data disposal route of the embodiment of the present invention, alternatively, also comprise: according to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, adopt terrain data to produce footmark image orthorectify product; Judge that the footmark image that cloud and mist value does not exceed preassigned is cloudless, then feature constraint condition judgment is carried out to echo waveform characteristic parameter; If meet described feature constraint condition, be then combined to form laser height reference mark with described laser footmark point accurate three-dimensional coordinate and described footmark image orthorectify product.

According to the cloud and mist quantity measuring method of the earth observation laser footmark image of the embodiment of the present invention, to detect based on cloud and mist amount and the extracting method at earth observation laser height reference mark of echo waveform process and laser-measured height satellite data disposal route, the impact of cloud layer on laser ranging can be reduced, ensure the precision of laser ranging, effectively improve the accuracy of laser height reference data.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, be briefly described below by the accompanying drawing of embodiment, apparently, the accompanying drawing in the following describes only relates to some embodiments of the present invention, but not limitation of the present invention.

Fig. 1 is the process flow diagram of the cloud and mist quantity measuring method of laser footmark image according to the embodiment of the present invention;

Fig. 2 schematically shows according to the meticulous extraction flow process in the laser height reference mark of the embodiment of the present invention;

Fig. 3 A is the tight geometry location model schematic of laser-measured height satellite, and Fig. 3 B is the angle schematic diagram of Laser emission direction and body coordinates system;

Fig. 4 A and Fig. 4 B schematically show the transmitted waveform of laser ceilometer and receives waveform;

Fig. 5 schematically shows the treatment scheme of spaceborne laser altimeter system data according to an embodiment of the invention;

Fig. 6 schematically shows the staging hierarchy of laser-measured height satellite data product;

Fig. 7 shows the schematic production procedure of basic product;

Fig. 8 shows the schematic production procedure of standardized product;

Fig. 9 shows the schematic production procedure of thematic product/high-grade products.

Embodiment

For making the object of the embodiment of the present invention, technical scheme and advantage clearly, below in conjunction with the accompanying drawing of the embodiment of the present invention, the technical scheme of the embodiment of the present invention is clearly and completely described.Obviously, described embodiment is a part of embodiment of the present invention, instead of whole embodiments.Based on described embodiments of the invention, the every other embodiment that those of ordinary skill in the art obtain under without the need to the prerequisite of creative work, all belongs to the scope of protection of the invention.

Unless otherwise defined, technical term used herein or scientific terminology should be in field belonging to the present invention the ordinary meaning that the personage with general technical ability understands." first ", " second " that use in patent application specification of the present invention and claims and similar word do not represent any order, quantity or importance, and are only used to distinguish different ingredients.Equally, the similar word such as " " or " " does not represent restricted number yet, but represents to there is at least one.

China plans the civilian stereoplotting satellite of 1:1 ten thousand high precision launched in 2018, and it will carry a set of laser-measured height system.This laser-measured height system, as auxiliary loads, for the optical image simultaneous adjustment of taking with CCD camera, reaches and promotes the object of high-resolution satellite without control positioning precision.This cover laser-measured height system also will be equipped with footmark camera, can obtain the footmark image that pulse arrives ground formation, thus can determine the actual position of footmark, overcome the problem that laser-measured height System planes positioning error is large.Such as, laser-measured height system adopts wavelength to be the laser pulse of 1064nm, this wavelength is in atmospheric window wave band, good penetrability is had to air, but when facing the situation of cloud block or dense fog, laser cannot penetrate cloud and mist and arrive ground, and the footmark position thus obtained may be the position on cloud and mist surface, such data do not reach observation requirement, be rejected.

Alternatively, can by the high data of survey obtained and existing digital elevation model (DEM) be contrasted, measurement data gap being exceeded certain threshold value judges to think that the footmark point measured is positioned on cloud and mist, thus rejects.But this method is for there being certain limitation, on the one hand the precision of DEM be there are certain requirements, arrive ground at laser energy partial penetration cloud and mist on the other hand, and when can receive ground echo signal, this algorithm easily lost efficacy, and can not reflect the reliability of laser ranging value exactly.

Laser ranging data extracting method according to the embodiment of the present invention screens laser ranging data based on the testing result of cloud and mist amount.Utilize footmark image, adopt the thought of classification of remote-sensing images to carry out cloud and mist and detect differentiation, can also further combined with return laser beam waveform character, if when footmark path existing cloud and dense fog, and echo waveform peak value is less, broadening is larger then thinks that measurement data exists compared with big error or unavailable.

Below illustrate the method utilizing footmark image to carry out the detection of cloud and mist amount.The cloud and mist amount detection of remote sensing image is exactly the classification of image in essence, cloud and mist is regarded as the one of many atural object.Generally speaking, cloud and mist amount detects what rely on is two features of cloud and mist: spectral signature and textural characteristics.Spectral signature reflection cloud cluster, in the radiation reflective situation of different-waveband, comprises the radiation characteristic of cloud and the reflective spectral property of cloud and atural object.Textural characteristics can be considered to, in subrange, and the space distribution of the inter-stages such as gradation of image and the interaction in space thereof.

Because the footmark image of laser-measured height system does not comprise multispectral information, according to the present invention, consider the cloud and mist detection method utilizing footmark panchromatic image, alternatively, adopt the threshold method based on grey level histogram and the detection method based on gray level co-occurrence matrixes to detect cloud and mist.Further, for promoting the accuracy rate that cloud and mist detects, comprehensively these two kinds of methods cloud and mist differentiation can be carried out.

What grey level histogram reflected is the frequency that in a sub-picture, each gray-level pixels occurs, take gray level as horizontal ordinate, with the frequency of gray level for ordinate, it is a key character of image, reflects the situation of gradation of image distribution.When the grey level histogram of whole footmark image exists obvious two peak, then show that the brighter areas of this image can be separated preferably with comparatively dark areas, using these two peak values as with reference to setting threshold value, good binary Images Processing effect can be obtained.

Obtain the optimal threshold of the grey value characteristics of cloud and mist through a certain amount of remote sensing image sample training, in the grey level histogram of view picture remote sensing image, when threshold value is in certain frequency, can differentiate there is cloud.Utilize grey level histogram can judge on the whole containing cloud amount.Be some subgraph blocks by Image Segmentation, its gray average is added up to each subgraph block, according to the size of average, tentatively realize cloud and mist and judge.

Because the intensity profile of cloud on image is even, saltus step degree is little, texture is thicker and fuzzy, and with the feature similarity of part atural object, the textural characteristics in such as desert and stratus is very close.In order to increase the accuracy that cloud and mist detects, histogram equalization can be carried out to image and strengthening process, outstanding implicit grain details.The formula of equalization is as follows:

$s_k=T\left(r_k\right)=\underset{i=0}{\overset{k}{\&Sigma;}}{P}_r\left(r_i\right)=\underset{r=0}{\overset{k}{\&Sigma;}}\frac{n_i}{n}$

0≤r _k≤1,k＝0,1,2,...L-1

In above formula, s _kfor the new gray-scale value of pixel after conversion that former figure gray-scale value is k; P _r(r _i) dot frequency of to be gray-scale value be i; The gray shade scale of L and image.

On the other hand, texture can be considered to, in subrange, and the space distribution of the inter-stages such as gradation of image and the mutual relationship in space thereof.Gray level co-occurrence matrixes obtains the statistics of the specific gray scale keeping two of certain distance pixels to have respectively with image, it can reflect the distribution character of gray scale, also can reflect simultaneously have same gray scale or close to same gray scale pixel between position distribution characteristic, a kind of method based on gradation of image joint probability matrix, namely about the second-order statistics feature of variation of image grayscale.Due to the detection that cloud and mist detection is based on footmark image greyscale value, therefore cloud detection scheme can use gray level co-occurrence matrixes as the foundation of its feature extraction.

Gray level co-occurrence matrixes be from image intensity value be i pixel (x, the y), statistics with its distance be d, gray-scale value is the frequency P (i, j, d, θ) that the pixel (x+a, y+b) of j occurs simultaneously, and mathematic(al) representation is:

P(i,j,d,θ)＝{[(x,y),(x+a,y+b)|f(x,y)＝i；f(x+a,y+b)＝j]}

Wherein, θ is the generation direction of gray level co-occurrence matrixes.Briefly, d and θ determines position and the direction of two pixels, can draw gray level co-occurrence matrixes P under the condition that both are certain:

$P=\left(\begin{array}{ccc}P(0,0)& ...& P(0,L-1)\\ ...& ...& ...\\ P(L-1,0)& ...& P(L-1,L-1)\end{array}\right)$

Wherein each element P (i, j) represents the number of times that gray scale i and gray scale j occurs at given position and direction, and L represents number of greyscale levels.The value obtaining 4 directions is only needed to represent veined information.

Following 4 characteristic quantity f can be used ₁, f ₂, f ₃, f ₄as textural characteristics:

(1) angle second moment f ₁

$f_1=ASM=\underset{i=1}{\overset{L}{\&Sigma;}}\underset{j=1}{\overset{L}{\&Sigma;}}{P}^2(i,j)$

Reflect the homogeneity of image distribution and the fineness of texture: when most elements distribution is near principal diagonal, key diagram is comparatively even as intensity profile, and now texture is relatively thicker, so f ₁value can be larger; Otherwise f ₁time less, illustrate that texture is thinner.

(2) homogeney f ₂

$f_2=IDM=\underset{i=1}{\overset{L}{\&Sigma;}}\underset{j=1}{\overset{L}{\&Sigma;}}\frac{P(i,j)}{1+{(i-j)}^2}$

Unfavourable balance square reflects the homogeney of image texture, if image local texture lacks change very evenly, then this value can be larger.

(3) contrast f ₃

$f_3=\underset{n=1}{\overset{L}{\&Sigma;}}{n}^2\left(\underset{i=1}{\overset{L}{\&Sigma;}}\underset{j=1}{\overset{L}{\&Sigma;}}P\right(i,j\left)\right)$

Wherein | i-j|=n, picture contrast reflects the sharpness of texture.In image, if the right gray scale difference of pixel is larger, so the contrast of texture is stronger, and visual effect is more obvious.Otherwise then show that texture is not obvious.Often coarse texture contrast is smaller, so contrast also can reflect the fineness of texture.

(4) correlativity f ₄

$f_4=COR=\frac{\underset{i=1}{\overset{L}{\&Sigma;}}\underset{j=1}{\overset{L}{\&Sigma;}}(i-j)P(i,j)-{\mathrm{\&mu;}}_x{\mathrm{\&mu;}}_y}{{\mathrm{\&sigma;}}_x{\mathrm{\&sigma;}}_y}$

Wherein,

${\mathrm{\&mu;}}_x=\underset{i=1}{\overset{L}{\&Sigma;}}i\underset{j=1}{\overset{L}{\&Sigma;}}P(i,j),{\mathrm{\&mu;}}_y=\underset{i=1}{\overset{L}{\&Sigma;}}j\underset{j=1}{\overset{L}{\&Sigma;}}P(i,j)$

${\mathrm{\&sigma;}}_x=\underset{i=1}{\overset{L}{\&Sigma;}}{(i-{\mathrm{\&mu;}}_x)}^2\underset{j=1}{\overset{L}{\&Sigma;}}P(i,j),{\mathrm{\&sigma;}}_y=\underset{i=1}{\overset{L}{\&Sigma;}}{(j-{\mathrm{\&mu;}}_y)}^2\underset{j=1}{\overset{L}{\&Sigma;}}P(i,j)$

The direction of correlativity reflection texture, it has been weighed gray level co-occurrence matrixes element and has been expert at or the similarity of column direction.If certain gray scale is longer at a direction development length, then relevance values is larger in this direction.When texture region similar in piece image has certain directivity, its relevance values is larger.

Utilize a large amount of containing cloud and mist image as training sample, obtain the textural characteristics of cloud and mist, as the threshold value that cloud and mist amount differentiates, preferably adopt angle second moment as textural characteristics.

So by grey level histogram and gray level co-occurrence matrixes two kinds of methods combining, the cloud and mist carrying out footmark image detects, and step is as follows:

Utilize a large amount of cloud and mist images that contains to carry out sample training, obtain preferred gray threshold and the textural characteristics value of cloud and mist;

Calculate the grey level histogram of view picture footmark image, tentatively judge whether to there is cloud and mist, and the content of cloud and mist, alternatively, the enhancing of gray-scale value equalization is carried out to footmark image;

Calculate the gray average of the sub-block of footmark image, determine whether to comprise cloud and mist according to this average, such as, gray scale higher than 235 representative containing cloud and mist, lower than 80 not containing cloud and mist, the image sub-block be between two threshold values is further detected;

Utilize the textural characteristics being in the image sub-block between two threshold values described in gray level co-occurrence matrixes calculating, the cloud and mist textural characteristics value obtained with sample training contrasts;

Statistics is judged as the sum of all pixels of cloud and mist and the quantity accounting (number percent) in footmark image thereof, determines cloud and mist amount.

Fig. 1 schematically shows the step of above-mentioned laser footmark image cloud and mist quantity measuring method.

Based on above-mentioned laser footmark image cloud and mist quantity measuring method, according to embodiments of the invention, propose a kind of laser ranging value efficiency assessment method based on the cloud detection of footmark image.

The basic procedure of this laser ranging value efficiency assessment method is as follows:

What pass down for laser-measured height satellite carries out system Geometric correction and preliminary waveform processing through decoded raw data, according to geometrical correspondence, obtain the footmark image that laser facula is corresponding, realize the basic registration of laser and footmark image based on hardware parameter and geographic coordinate.If done the preliminary demarcation of footmark camera and laser ceilometer, also calibration result can be directly used in the registration of laser and footmark image.

Because the image of footmark camera acquisition is much larger than the actual ground footmark size of laser, therefore need to do certain cutting.Determine the center position of the footmark image corresponding with laser facula of above-mentioned acquisition, and determine the area S=π R that in footmark image, laser facula is corresponding ², wherein R is the radius of ground laser footmark, considers laser guide precision, R can be expanded and be twice, to ensure all standing of footmark image to laser footmark point.The image determined is carried out cutting or stored in forming footmark image blocks in internal memory.

Adopt aforesaid cloud and mist amount detection algorithm, the detection of cloud and mist amount is carried out to footmark image blocks, obtain the cloud and mist value of footmark image blocks, and based on this cloud and mist value, cloud and mist situation is judged, such as, if cloud and mist amount <10%, be judged to be cloudless, cloud and mist amount >10% and <30% is then judged to be Bao Yun, if cloud and mist amount >30%, be judged to be spissatus.

Validity or the availability of the laser ranging value of footmark image blocks can be judged afterwards according to cloud and mist value.Such as, by being judged to be that the laser ranging value of cloudless footmark image blocks is labeled as excellent, the laser ranging value of the footmark image blocks being judged to be Bao Yun being labeled as good, will being judged to be that the laser ranging value of spissatus footmark image blocks is labeled as difference.Further, be labeled as excellent laser ranging value completely available, be labeled as good laser ranging value and can be considered stand-by, be labeled as poor completely unavailable, do not participate in the production of subsequent product.

An important application of laser-measured height satellite is exactly the high-precision vertical control point data that can obtain global range, but the final vertical accuracy of the ground footmark point of laser-measured height satellite is except the distance accuracy impact of Stimulated Light device own, also with satellite position and attitude measurement accuracy, atmospheric effect, the factors such as surface irregularity size are relevant, therefore must demarcate through precise geometrical, atmospheric correction, laser height reference point after the process such as tide correction combines relevant auxiliary parameter and screens, ensure that the reliable laser height reference data of final reservation is as thematic product.In conjunction with the aforesaid laser ranging value efficiency assessment method based on the cloud detection of footmark image, according to embodiments of the invention, further provide a kind of laser height Control point extraction method of MULTIPLE PARAMETERS CONSTRAINT, to realize effective production of laser height reference mark special topic product.

The basic step of the laser height Control point extraction method of this MULTIPLE PARAMETERS CONSTRAINT is as follows:

Retain the laser ranging value being judged to be cloudless footmark image blocks, weed out the laser height data being judged to be thin cloud or spissatus footmark image blocks;

Because received pulse energy is subject to atmospheric backscatter, sun veiling glare, the impact such as over-exposed, therefore determine the reflectivity ε <1 of laser footmark point (wherein ) as screening parameter, screen the laser footmark point in above-mentioned laser height data;

And select in echo waveform, only there is a crest, i.e. nPeaks=1, peak E is greater than certain threshold value V (concrete threshold value need be determined according to parameters such as the emitted energy of laser instrument and Receiver apertures), and the laser footmark point of standard deviation sigma≤3.2ns after waveform fitting;

The laser footmark point that obtains after screening, as laser height reference mark, is combined its footmark image, builds laser height reference mark database.

Fig. 2 schematically shows according to the meticulous extraction flow process in the laser height reference mark of the embodiment of the present invention.In the flow process shown in Fig. 2, improve the degree of accuracy of laser height Control point extraction further combined with landform reference data and footmark image orthorectify product.

Defining and approximating method of following explanation earth observation laser-measured height satellite echo waveform.

In order to reflect the vertical distribution of atural object more accurately, disclose geometry and the physical attribute of atural object, the laser-measured height satellite of earth observation is generally with the sampling interval (as 1GHz) such as very little, in chronological sequence sequentially sample record is carried out to the back scattering energy that Emission Lasers pulse and interacting goals are formed, obtain a time dependent echoed signal, this echoed signal is called as echo waveform data.Echo waveform comprises the characteristic informations such as amplitude, pulsewidth, crest number, backscattering cross, carries out wave f orm analysis, also can form the important step of of laser-measured height Data processing based on echo waveform data.

The ultimate principle of laser-measured height satellite is: by satellite launch laser beam after ground return by satellite reception, calculate the time interval t of Laser emission and reception, the velocity of propagation of light is c, then laser one way transmission range p=c*t/2, then the satellite position obtained in conjunction with the GPS that satellite carries and star sensor and attitude information, can obtain the dimensionally areal coordinate of laser footmark point.Its tight geometric model as shown in Figure 2, wherein P _laserfor the reference point of Laser emission, P _gPSfor gps antenna phase center, O _bodyfor the initial point of centroid of satellite or body coordinate system, P _groundfor laser ground footmark point.

The original rail attitude parameter measurement of satellite all defines under international Celestial Reference System system ICRS (InternationalCelestialReferenceSystem), and International Celestial Reference System reference frame ICRF (InternationalCelestialReferenceFrame) is the specific implementation of ICRS, main employing J2000 coordinate system at present.The Three Dimensional Ground coordinate of usual description is undefined at International Geophysical reference frame ITRS (InternationalTerrestrialReferenceSystem), as the WGS84 coordinate system best with ITRF2000 degree of conformity, wherein ITRF is the specific implementation of ITRS.The coordinate conversion matrix of International Celestial Reference System reference frame ICRF to International Terrestrial Reference Frame ITRF is relevant with earth rotation, the precession of the equinoxes, nutating etc., wherein P (t) is precession of the equinoxes matrix, and N (t) is nutating matrix, and R (t) is earth rotation matrix, and W (t) is Ghandler motion matrix.

Satellite body coordinate system is defined as: centroid of satellite is initial point, and X-axis points to satellite flight direction, and Z axis points to zenith direction, and Y-axis, perpendicular to satellite orbit plane, forms right-handed coordinate system with X, Z axis, as shown in Figure 3A.During Laser emission there is certain angle in pointing direction and satellite body coordinate system, supposes that the negative sense angle of laser guide and body coordinate system Z axis is θ, and the projection in XOY plane and X-axis forward angle are α, as shown in Figure 3 B.

If the distance measurement value of laser is ρ, the coordinate of reference laser light point in body coordinate system is: at the coordinate of laser footmark point under satellite body coordinate system be then:

$\stackrel{\&OverBar;}{\mathrm{\&rho;}}=\left(\begin{array}{c}Lx\\ Ly\\ Lz\end{array}\right)+{\left(\begin{array}{c}\mathrm{\&rho;}sin\mathrm{\&theta;}cos\mathrm{\&alpha;}\\ \mathrm{\&rho;}sin\mathrm{\&theta;}sin\mathrm{\&alpha;}\\ -\mathrm{\&rho;}cos\mathrm{\&theta;}\end{array}\right)}_{Body}$

The phase center of GPS generally not exclusively overlaps with centroid of satellite, there is certain deviation between the two, assuming that the coordinate of the phase center of GPS under satellite body coordinate system is: rotation matrix between Satellite sensor body coordinate system and satellite body coordinate is the rotation matrix that what star sensor recorded is under the quick body of star is tied to J2000 coordinate system

Therefore, the tight geometry location formula of laser-measured height satellite is:

${\left(\begin{array}{c}X\\ Y\\ Z\end{array}\right)}_{ITRF}=R_{J2000}^{ITRF}\&lsqb;{\left(\begin{array}{c}{X}_{GPS}\\ Y_{GPD}\\ Z_{GPS}\end{array}\right)}_{J2000}+R_{Star}^{J2000}{R}_{Body}^{Star}\&lsqb;\left(\begin{array}{c}Lx\\ Ly\\ Lz\end{array}\right)+\left(\begin{array}{c}(\mathrm{\&rho;}+\mathrm{\&Delta;}\mathrm{\&rho;})\sin \mathrm{\&theta;}\cos \mathrm{\&alpha;}\\ (\mathrm{\&rho;}+\mathrm{\&Delta;}\mathrm{\&rho;})\sin \mathrm{\&theta;}\sin \mathrm{\&alpha;}\\ -(\mathrm{\&rho;}+\mathrm{\&Delta;}\mathrm{\&rho;})\cos \mathrm{\&theta;}\end{array}\right)-\left(\begin{array}{c}Dx\\ Dy\\ Dz\end{array}\right)\&rsqb;\&rsqb;$

Wherein Δ ρ is the range finding corrected value caused because of atmospheric refraction and hardware error.

Rectangular space coordinate (X, Y, Z) under Terrestrial Reference Frame coordinate system ITRF is shown below with the corresponding relation between longitude and latitude (B, L) and geodetic height H.

$\left\{\begin{array}{c}X=(N+H)\cos B\cos L\\ Y=(N+H)\cos B\sin L\\ Z=\&lsqb;N(1-e^2)+H\&rsqb;\sin B\end{array}\right.$

In above formula, N is this prime vertical radius, and e is reference ellipsoid first excentricity.The computing formula of N is:

$N=\frac{a}{\sqrt{1-e^2{\sin }^{2}B}}$

Wherein, a is reference ellipsoid major semi-axis.

Because laser ceilometer transmitted waveform can be approximately Gauss pulse, laser can be similar to through ground surface reflection back echo waveform the superposition regarding one or many Gauss pulse as.Fig. 4 A and Fig. 4 B schematically show the transmitted waveform of laser ceilometer and receives waveform.

For many echo waveforms data, the mode adopting multiple Gaussian function to superpose carries out matching, and fitting formula is shown below.

$w\left(t\right)=\mathrm{\&epsiv;}+\underset{m=1}{\overset{p}{\&Sigma;}}{A}_m{e}^{(-\frac{{(t-t_m)}^2}{2{{\mathrm{\&sigma;}}_m}^2})}---\left(2.14\right)$

In above formula, t is the time, A _m, t _m, σ _mbe respectively the amplitude of m Gaussian function, average and standard deviation, ε is wave noise value.

3 parameter availability vector forms of the Gaussian function model of echo waveform are expressed as

c _m＝[A _m,t _m,σ _m](2.15)

Then unknown number availability vector is expressed as X, and the dimension of X is 3p+1.

X＝[ε,c ₁,c ₂,…,c _p] ^T

The number of samples of setting echo waveform is N, and for GLAS, N=544, then the actual ghosts value of each sampled point is expressed as: R=[r ₁, r ₂..., r _n] ^t(2.16)

The value of the waveform model that each sampled point that employing formula (2.14) calculates is corresponding is

W＝[w ₁,w ₂,...,w _N] ^T(2.17)

The calculated value error l of definition sampled value and waveform model is

F(C)＝W-R(2.18)

Unknown parameter vector C, i.e. F (C)=0 during optimization in order to Confirming model;

To the waveform model of (2.14), unknown parameter vector C local derviation is asked to obtain:

$A=\frac{\&part;W}{\&part;C}=\left[\begin{array}{cccc}\frac{\&part;w_1}{\&part;\mathrm{\&epsiv;}}& \frac{\&part;w_1}{\&part;c_1}& \mathrm{...}& \frac{\&part;w_1}{\&part;c_p}\\ \frac{\&part;w_2}{\&part;\mathrm{\&epsiv;}}& \frac{\&part;w_2}{\&part;c_1}& \mathrm{...}& \frac{\&part;w_2}{\&part;c_p}\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ \frac{\&part;w_N}{\&part;\mathrm{\&epsiv;}}& \frac{\&part;w_N}{\&part;c_1}& \mathrm{...}& \frac{\&part;w_N}{\&part;c_p}\end{array}\right]---\left(2.19\right)$

Waveform model first order Taylor formula is launched:

$w_n^{j+1}=w_n^j+\frac{\&part;w_n^j}{\&part;\mathrm{\&epsiv;}}{\mathrm{\&delta;}}_{\mathrm{\&epsiv;}}+\underset{m=1}{\overset{p}{\&Sigma;}}\frac{\&part;w_n^j}{\&part;c_m}{\mathrm{\&delta;}}_{c_m}---\left(2.20\right)$

Wherein:

$\frac{\&part;w_n}{\&part;\mathrm{\&epsiv;}}=1$

$\frac{\&part;w_n}{\&part;c_m}=\&lsqb;\frac{\&part;w_n}{\&part;L},\frac{\&part;w_n}{\&part;t_m},\frac{\&part;w_n}{\&part;{\mathrm{\&sigma;}}_m}\&rsqb;$

$\frac{\&part;w_n}{\&part;A_m}=\exp \&lsqb;-\frac{{(t-t_m)}^2}{2{{\mathrm{\&sigma;}}_m}^2}\&rsqb;$

$\frac{\&part;w_n}{\&part;t_m}=\frac{A_m(t-t_m)}{{{\mathrm{\&sigma;}}_m}^2}\exp \&lsqb;-\frac{{(t-t_m)}^2}{2{{\mathrm{\&sigma;}}_m}^2}\&rsqb;=\frac{A_m(t-t_m)}{{{\mathrm{\&sigma;}}_m}^2}\frac{\&part;w_n}{\&part;A_m}$

$\frac{\&part;w_n}{\&part;{\mathrm{\&sigma;}}_m}=\frac{A_i{(t-t_i)}^2}{{{\mathrm{\&sigma;}}_m}^3}\exp \&lsqb;-\frac{{(t-t_i)}^2}{2{{\mathrm{\&sigma;}}_m}^2}\&rsqb;=\frac{(t-t_m)}{{\mathrm{\&sigma;}}_m}\frac{\&part;w_n}{\&part;t_m}---\left(2.21\right)$

For formula (2.18),

There is F (C)=W (C)+A δ x-R,

Wherein, W (C) is the echo approximate value calculated according to solve for parameter C and model (2.14).

Constraint condition is: F (C)=0, then have

Aδx＝L

L＝R-W(C)(2.22)

Then δ x=[A ^ta] ^-1a ^tl, wherein , consider weight and priori value, formula can be written as:

δx＝[A ^TPA+V ₀] ^-1A ^TPL(2.23)

Wherein: P is weight matrix, V ₀for priori value matrix, P _ij=p _iδ _ij, [V ₀] _jk=p _ckδ _jk, p _ithe weight of i-th sampled value, p _ckfor a kth vectorial c _kpriori value weight.

Wherein, δ _ijfor the kronecker δ function value:

${\mathrm{\&delta;}}_{ij}=\left\{\begin{array}{c}0,i\&NotEqual;j\\ 1,i=j\end{array}\right.$

After calculating δ x, new parameter can be obtained:

C ⁱ⁺¹＝C ⁱ+δx(2.24)

Judging | δ x|<d, wherein d is the threshold value of setting.If set up, then stop iteration, output parameter C; If be false, then adopt new parameter C, get back to (2.18) and carry out next iteration computing.

Detect and echo waveform data processing in conjunction with above-mentioned footmark image cloud and mist, earth observation laser-measured height satellite data treatment scheme can be described as:

1), denoising smoothing to the transmitting and receiving waveform of laser, extracts waveform feature parameter, determines to transmit and receive moment corresponding to waveform center of gravity, according to the Laser Transmission time interval, calculates laser one-way transmission initial distance value;

2) according to Satellite Attitude rail parameter, laser emission time, initial distance value and laser geometric location model, the rough three-dimensional coordinate of laser footmark point is calculated;

3) according to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, footmark image geometric rough correct product is produced in resampling;

Wherein, the waveform feature parameter that above-mentioned 1 ~ 3 step obtains, the rough three-dimensional coordinate of laser initial distance value laser footmark point, footmark image geometric rough correct product are basic product, need to process all laser data points,

4) adopt cloud and mist detection model to process to footmark image, obtain footmark image cloud and mist testing product;

5) if cloud and mist amount exceeds standard (as ratio surpasses 20%) in footmark image cloud and mist testing product, then the process that the 4th step carries out next laser spots is got back to; If cloud and mist amount does not exceed standard, enter the 6th step;

6) adopt atmospheric delay correction model, obtain atmospheric delay correction value according to the rough three-dimensional coordinate of the laser footmark point in atmospheric parameter and the 2nd step;

7) according to laser distance measuring system error amount, the initial distance value in the 1st step, the atmospheric delay correction value in the 6th step that geometry calibration obtains, accurate distance value is calculated;

8) according to Satellite Attitude rail parameter, laser emission time, accurate distance value and laser geometric location model, laser footmark point three-dimensional coordinate is calculated;

9) adopt tide correction model, calculate tidal difference, the result in the 8th step is revised, obtain laser footmark point accurate three-dimensional coordinate;

10) according to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, terrain data is adopted to produce footmark image orthorectify product;

Wherein, the footmark image cloud and mist testing product that above-mentioned 4 ~ 10 steps obtain, atmospheric delay correction value, accurate distance value, tidal difference, the accurate three-dimensional coordinate of laser footmark point, footmark image orthorectify product are standardized product,

11) the footmark image cloud and mist testing product that cloud and mist amount in the 5th step does not exceed standard is judged, if cloudless, then enter the 12nd step; Otherwise, enter the 17th step;

12) feature constraint condition judgment (such as adopting aforesaid echo waveform matching) being carried out to echo waveform characteristic parameter, as met, then entering the 13rd step; Otherwise, enter the 16th step;

13) utilize laser footmark point accurate three-dimensional coordinate and the footmark image orthorectify product of the 9th step and the 10th step, be combined to form laser height reference mark;

14) utilize the laser height reference point obtained with the many phase measurements in region to carry out elevation mutation analysis, obtain polar ice sheet variation monitoring product;

15) the laser height reference point utilizing many rails to measure acquisition builds database, forms storehouse, laser height reference mark product;

16) analysis of forestry parameter extraction is carried out to return laser beam waveform feature parameter, obtain forestry special topic product;

17) cloud amount is analyzed, in conjunction with the 9th, the result of 10 steps, obtain other classes special topic products.

Wherein, the 14 to 17 step produces polar ice sheet variation monitoring product, storehouse, laser height reference mark product, forestry special topic product, other classes special topic products all belong to the thematic class high-grade products by processing generation further.

Fig. 5 schematically shows the treatment scheme of spaceborne laser altimeter system data according to an embodiment of the invention.Such as, according to Satellite Attitude rail parameter and camera basic parameter, set up the footmark image after system geometry correction, according to Satellite Attitude rail parameter, laser guide parameter, the approximate location of laser initial ranging value determination laser facula in footmark image.

Fig. 6 schematically shows the staging hierarchy of laser-measured height satellite data product.Be described as follows:

Level_0 (0 grade) raw data product: refer to that laser-measured height satellite passes down through decoded raw data, comprise laser footmark image, satellite attitude measurement data, satellite orbit measurement data, laser emitting waveform data, return laser beam Wave data and related hardware parameter etc.There is provided, only for surface data handling system outside raw data product general tree.

Level_1 (1 grade) basic product: pointer is to the product of raw data product after system Geometric correction and preliminary waveform processing, comprise the characteristic parameter of waveform, the rough distance parameter of laser, footmark image geometric rough correct product, the rough three-dimensional coordinate of laser footmark etc., wherein the appearance rail parameter after accurate process is afterwards classified as basic product.There is provided outside basic product general tree, only for surface data handling system.

The schematic production procedure of basic product is such as shown in Fig. 7.Production procedure as shown in Figure 7, the product obtained is: waveform feature parameter, laser initial distance value, laser footmark point just omit three-dimensional coordinate, footmark image geometric rough correct product.In this production phase, by the production requirement of product, as long as form is complete, data do not lack, all should produce, just add quality inspection later, poor for the quality of data is marked, will not issue.

Level_2 (2 grades) standardized product: refer to the product after the process such as precise geometrical demarcation, atmospheric correction, tide correction, comprise atmospheric correction parameter, tide correction parameter, footmark image cloud detection product, footmark image orthorectify product, laser footmark accurate three-dimensional coordinate product.Standardized product can be issued user.

The schematic production procedure of standardized product is such as shown in Fig. 8.Production procedure as shown in Figure 8, the product obtained is: atmospheric delay correction parameter, tide correction parameter, accurate distance value, laser footmark three-dimensional coordinate, footmark image cloud detection product, footmark image orthorectify product.

Level_3 (3 grades) thematic product/high-grade products: refer on the basis of standardized product, for the laser-measured height satellite high-grade products of user's particular demands exploitation, comprise storehouse, laser height reference mark product, forestry special topic product, polar ice sheet monitoring product, other class special topic products etc.Special topic product can be issued user.

The schematic production procedure of special topic product/high-grade products is such as shown in Fig. 9.Production procedure as shown in Figure 9, the product obtained is: polar ice sheet monitoring product, storehouse, laser height reference mark product, forestry special topic product, other class special topic products.

Wherein, aforesaid laser ranging value efficiency assessment method may be used for the subsequent treatment of 1 grade and 2 DBMSs (product); The laser height Control point extraction method of aforesaid MULTIPLE PARAMETERS CONSTRAINT may be used for the subsequent treatment of 2 DBMSs (product).

Application laser-measured height satellite carries out the research of global vertical control point acquisition, can in present stage for China provides a kind of technological means obtaining land vertical control point overseas; For China's whole world mapping provides vertical control point Data safeguard; The accuracy for vertical control obtaining and improve the domestic ground control point of China on a large scale can also be used in addition, for other remote sensing equipment provides calibration data; Finally can also promote the positioning precision of domestic remote sensing satellite data further, widen the application of domsat data.

According to the cloud and mist quantity measuring method of the earth observation laser footmark image of the embodiment of the present invention, to detect based on cloud and mist amount and the earth observation laser height Control point extraction method of echo waveform process and laser-measured height satellite data disposal route, the impact of cloud layer on laser ranging can be reduced, ensure the precision of laser ranging, effectively improve the accuracy of laser height reference data.

The above is only exemplary embodiment of the present invention, but not for limiting the scope of the invention, protection scope of the present invention is determined by appended claim.

Claims (10)

1. a cloud and mist quantity measuring method for laser footmark image, is characterized in that, comprising:

Utilize a large amount of cloud and mist images that contains to carry out sample training, obtain preferred gray threshold and the textural characteristics value of cloud and mist;

Calculate the grey level histogram of view picture footmark image, tentatively judge whether to there is cloud and mist based on described preferred gray threshold, and the content of cloud and mist;

Calculate the gray average of the sub-block of footmark image, when the gray average of described sub-block is higher than judging containing cloud and mist during first threshold, when the gray average of described sub-block is lower than judging not containing cloud and mist during Second Threshold;

Utilize gray level co-occurrence matrixes calculating gray average to be in the textural characteristics of the image sub-block between described first threshold and Second Threshold, contrast with the described cloud and mist textural characteristics value obtained from described sample training;

Statistics is judged as the sum of all pixels of cloud and mist and the quantity accounting in described view picture footmark image thereof, determines cloud and mist amount.

2. cloud and mist quantity measuring method according to claim 1, is characterized in that, when calculating the grey level histogram of view picture footmark image, carry out histogram equalization to image and strengthen process, the formula of equalization is as follows:

$s_k=T\left(r_k\right)=\underset{i=0}{\overset{k}{\&Sigma;}}{P}_r\left(r_i\right)=\underset{i=0}{\overset{k}{\&Sigma;}}\frac{n_i}{n}$

0≤r _k≤1,k＝0,1,2,...L-1

Wherein, s _kfor the new gray-scale value of pixel after conversion that former figure gray-scale value is k; P _r(r _i) dot frequency of to be gray-scale value be i; L is the gray shade scale of image.

3. cloud and mist quantity measuring method according to claim 1, is characterized in that, during described first threshold 235, described Second Threshold is 80.

4. cloud and mist quantity measuring method according to claim 1, is characterized in that, the textural characteristics considered when utilizing gray level co-occurrence matrixes to calculate the textural characteristics of described image sub-block comprises: angle second moment, homogeney, one or more in contrast and correlativity.

5. an earth observation laser ranging value efficiency assessment method, is characterized in that, comprising:

What pass down for laser-measured height satellite carries out system Geometric correction and preliminary waveform processing through decoded raw data, according to geometrical correspondence, obtain footmark image corresponding to laser facula, the preliminary demarcation based on hardware parameter and geographic coordinate or footmark camera and laser ceilometer realizes the basic registration of laser and footmark image;

Determine the center position of the obtained footmark image corresponding with laser facula, and determine the area that in footmark image, laser facula is corresponding;

The image determined is carried out cutting or stored in forming footmark image blocks in internal memory;

Adopt the cloud and mist quantity measuring method according to any one of claim 1-4, the detection of cloud and mist amount is carried out to described footmark image blocks, obtain the cloud and mist value of footmark image blocks;

Validity or the availability of the laser ranging value of described footmark image blocks is judged based on described cloud and mist value.

6. a laser height Control point extraction method, is characterized in that, comprising:

Adopt earth observation laser ranging value efficiency assessment method according to claim 5, retain and be judged to be cloudless footmark image blocks, weed out the laser height data being judged to be thin cloud or spissatus footmark image blocks;

Using the reflectivity ε <1 of laser footmark point as screening parameter, screen the laser footmark point of the footmark image blocks of described reservation, wherein,

Select only there is a crest in echo waveform, peak value is greater than threshold value and the laser footmark point of standard deviation≤3.2ns after waveform fitting, wherein, for determining that the parameter of described threshold value comprises emitted energy and the Receiver aperture of laser instrument.

7. laser height Control point extraction method according to claim 6, is characterized in that,

The mode adopting multiple Gaussian function to superpose carries out waveform fitting to described echo waveform, and fitting formula is shown below:

$w\left(t\right)=\mathrm{\&epsiv;}+\underset{m=1}{\overset{p}{\&Sigma;}}{A}_m{e}^{(-\frac{{(t-t_m)}^2}{2{{\mathrm{\&sigma;}}_m}^2})}$

In above formula, t is the time, A _m, t _m, σ _mbe respectively the amplitude of m Gaussian function, average and standard deviation, ε is wave noise value.

8. an earth observation laser-measured height satellite data disposal route, is characterized in that, comprising:

, denoising smoothing to the transmitting and receiving waveform of laser, extracts waveform feature parameter, determines to transmit and receive moment corresponding to waveform center of gravity, according to the Laser Transmission time interval, calculates laser one-way transmission initial distance value;

According to Satellite Attitude rail parameter, laser emission time, initial distance value and laser geometric location model, calculate the rough three-dimensional coordinate of laser footmark point;

According to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, footmark image geometric rough correct product is produced in resampling;

Adopt the cloud and mist quantity measuring method according to any one of claim 1-4, carry out the detection of cloud and mist amount to footmark image, the laser footmark point cloud and mist value detected not being exceeded to the footmark image of preassigned is for further processing.

9. earth observation laser-measured height satellite data disposal route according to claim 8, is characterized in that, also comprise:

Adopt atmospheric delay correction model, obtain atmospheric delay correction value according to atmospheric parameter and the rough three-dimensional coordinate of described laser footmark point;

According to laser distance measuring system error amount, described initial distance value, described atmospheric delay correction value that geometry calibration obtains, calculate accurate distance value;

According to Satellite Attitude rail parameter, laser emission time, described accurate distance value and laser geometric location model, calculate laser footmark point three-dimensional coordinate;

Adopt tide correction model, calculate tidal difference, described calculating laser footmark point three-dimensional coordinate is revised, obtain laser footmark point accurate three-dimensional coordinate.

10. earth observation laser-measured height satellite data disposal route according to claim 9, is characterized in that, also comprise:

According to Satellite Attitude rail parameter, footmark image, footmark camera parameter and footmark image geometry location model, terrain data is adopted to produce footmark image orthorectify product;

If judge that the footmark image that described cloud and mist value does not exceed preassigned is cloudless, then feature constraint condition judgment is carried out to echo waveform characteristic parameter;

If meet described feature constraint condition, be then combined to form laser height reference mark with described laser footmark point accurate three-dimensional coordinate and described footmark image orthorectify product.