GB2336059A

GB2336059A - A multiple scale raster type map display

Info

Publication number: GB2336059A
Application number: GB9807292A
Authority: GB
Inventors: Han Ho Kim; Tae Hyo Ahn; Joong Chang Chun; Jin Soo Park; Yong Ho Yoon; Won Taik Hwang
Original assignee: KT Corp
Current assignee: KT Corp
Priority date: 1998-04-03
Filing date: 1998-04-03
Publication date: 1999-10-06
Also published as: GB9807292D0

Abstract

A raster type map display method displays various scales of stored raster type maps according to the display scale on screen. The scale of raster type map to be used is determined according to the display scale of the screen. If the region to be displayed does not have any corresponding scale of raster type map, the largest scale of raster type map among the lower and available scales of raster type maps is used for displaying. Also, different reference values for selecting a raster type map are used according to an expansion mode or reduction mode. Accordingly, a high display resolution can be effectively attained and the management of memory can be efficiently performed. In addition, processing speed is increased and the frequent replacement of the map is prevented.

Description

2336059 A RASTER TYPE MAP DISPLAY NETEOD

BACKGROUND OF THE INVENTION

The present invention relates to a display method of a raster type map for displaying one of various scale raster type maps, in accordance with the display ratio of a screen.

As computer has developed, the work having manually performed without any use of a computer is now performed using immense data storage capacity and marvelous speedy processing of a computer. GIS(Geographic Information System) is an example utilizing such immense data storage capacity and marvelous speedy processing of a computer. GIS is used to manage the infrastructure such as ducts for water service and for water spout and telephone lines and to utilize the information with regard to the geographical existence. In a work such as development of network design system related to the present invention, the accurate geographical information with regard to the region to be objected is a fatal factor. A raster type map is a representative example of this geographical information.

Raster type map means a data which is obtained by 1 raster-scanning a map. In other words, raster data is obtained by scanning the two-dimensional surface which is divided into mesh cell, as shown in Fig.1, each having one of two values or multi values. As one pixel on the picture i 1 taken by a satellite corresponds to one region specified, respectively, in a raster type map data, the geographical data is stored by pixel by a computer. In other words, raster type map is obtained by scanning paper map and then storing the scanned data by a computer.

Generally raster type map is made by scanning a certain scale of map. The scale of paper map to be really scanned is determined in accordance with the purpose of using raster type map. A raster.type map to be used for managing infrastructure such as ducts for water service and for water sewage, electric supply lines, telephone lines, etc. of a plurality of regions, is needed to be scale-reduced to 1/2,000 or smaller. Meanwhile, a raster type map to be used for region lay-out design or city lay-out design, etc., is needed to be scale-reduced to 1/10,000 or 1/100,000 or smaller. However, some system requiring detailed information of small street, house, building, etc., may often require the entire city-wide 2 region or the entire nation-wide region to the monitor screen.

In a conventional technology, as a raster type map is obtained by scanning only one paper map having a certain scale and then used, the following problems have been occurred. First of all, the scale of map to be displayed on computer screen varies depending on the zoom-in or zoom- out. If the scale of scanned map(raster type map) is 1/5,000 and the display scale is zoomed-in to 1/100, since the original map scale of 1/5, 000 is expanded and then displayed, the displayed character or line of the map is very thick and rough and the display for some character requires the entire screen. To the contrary, if the scale of the raster type map of 1/5,000 is zoomed-out to 1/100,000, the map on a screen should have immense data quantity because the map on the screen includes the original data of 1/5,000 scale map corresponding the screen-displayed region. Like this, large amount of data should be displayed on a screen, tremendous calculation is required in order to display the raster type map on the screen and move the display map within the screen, which results in the first problem that is 3 the speed of the system is reduced.

Also, in case that various scales of raster type maps are used, there is another problem that the various scaled raster type maps of all the regions should be prepared. In reality, this preparation is impossible. This is because it is difficult to obtain all the desired scale paper maps for all the regions. In addition, in some regions, large-scaled map is not necessary. Generally, while a small-scaled map such as 1/1,000,000 scaled map represents the entire region, a large-scaled map such as 1/500 scaled map is prepared only for some regions earnestly requiring it. The national map, for example 1/1,000,000 scaled map or 1/100,000 scaled map, should represent middle cities and small town, etc. as well as large cities, while 1/5,000 scaled map is generally necessary for the large cities such as Seoul and Pusan, etc. Therefore, in a specific display scale, some region has no corresponding scale of raster type map. In this case, the displayed screen represents null data, as shown in Fig.4A.

In the meanwhile, in case of the reference values T1, T2, T31... are used in determining the raster type map to be used, as the reference values are simple, even though 4 the displayed scale is little increased or decreased around the reference value, the raster type map may be replaced with another scale of raster type map. Accordingly, there is the third problem that the replacement of raster type map is too often made, to thereby reduce the speed of processing.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a raster type map display method to reduce the number of replacing the raster type map to be used, when the screen display scale is changed around reference values due to zooming-in or zooming-out operation.

To achieve the above object, the present invention provide a raster type map display method comprising first step for displaying a default scale of raster type map after initializing the display area and the raster type map; and a second step for displaying a scale of raster type map selected in accordance with display scale of a screen, among a plurality of raster type maps each having different scales.

In a raster type map display method according to the present invention, a plurality of raster type maps having various scales are used. Also, the scale of raster type map to be used is determined in accordance with display scale. If there is no corresponding raster type map, the largest scale of raster type map among the remnant raster type maps available each having a scale lower than the desired scale is selected. In addition, the criteria for selecting the raster type map is varied based on whether zoom-in mode or zoom-out mode.

Also, according to one aspect of the present invention, in the region not having the desired scale of raster type map, in order not to display null data on the screen corresponding to the region, the largest scale of raster type map is selected to be used among at least one raster type map having lower scale than the desired scale and corresponding the region.

According to the another aspect of the present invention, compound reference values is used, where the reference value is determined on the changing direction of zooming-in or zooming-out as well as the display scale of the screen.

6 is BRIEF DESCRIPTION OF THE DRAWING This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

Fig.1 shows the structure of a raster type data.

Fig.2 depicts the construction of a map display device to which the present invention is applicable.

Fig.3 shows an exemplary embodiment using raster type map which is selected based on the display scale.

Fig.4A and Fig.4B are for the explanation of a display method in which two region has different scale map.

Fig.5 is for the explanation of a modified raster type map display method using an upper reference value and a lower reference value.

Fig.6 shows the comparison results between compound reference value type and simple reference value type.

Fig.7 shows the overall flow of a raster type map display method according to the present invention.

Fig.8 is a detailed flowchart of determining the scale of raster type map in case of zooming-in according to the present invention.

Fig.9 is a detailed flowchart of determining the scale of 7 raster type map inzooming-out operation according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION is Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings.

Fig.2 is the drawing for showing the construction of a map display device to which the present invention is applicable. Reference numerals 21 represents a network server, 22 represents a central processing unit(hereinafter, it is simply mentioned to "CPU"), 23 represents a memory, 24 represents a hard disk, 25 represents a monitor, 26 represents a local area network(hereinafter, it is simply described to I'LAN11), 27 represents a client, 28 represents a scanner.

First, geographical image shown in a paper map is scanned by scanner 28 and then converted into a digital data. The digitized raster type map information is stored in hard-disk 24 of network server 21. The quantity of thus digitized raster type map is large, so the raster type map information should be stored in hard-disk 24 of network server 21 and clients 27 access the information through LAN 8 is 26 only when they need the information. When the raster type map corresponding to the desired region is displayed on monitor 25, CPU 22 reads the data corresponding to the region from hard-disk 24 to memory 23 and then displays them. At this time, since the capacity of memory 23 is fixed, if the data quantity of raster type map corresponding the region is too large, CPU 22 continually accesses hard disk 24. Generally, the access time for hard disk is much longer than the access time for memory. Accordingly, only the raster type information indispensable is read into memory 23 and unnecessary information is not read into memory so that the access time for hard disk should be reduced to the minimum time.

According to the present invention, the raster type map having a suitable data for the designated display scale is used so that the time for reading unnecessary information is reduced.

According to the present invention, a plurality of raster type maps are used. Each of raster type maps has different scales, respectively and corresponds to the 9 i is region to be displayed. That is, a plurality of paper maps each having different scales, are scanned and converted into a plurality of raster type maps to be used. At this time, the scale of raster type map to be used is determined on the display scale. For example, as shown in Fig.2, when the display scale is between reference value T1 and reference value T2.. a 1/100,000 scale of raster type map is used. When the display scale is between reference value T3 and reference value T,, a 1/5, 000 scale of raster type map is used. Thus, the first problem described above can be solved, so that the resolution of screen display is higher than that of the conventional technology using only one raster type map and the efficient memory management can be performed by displaying only the necessary information, which results in increasing the processing speed to a considerable high degree.

Fig.4A and Fig.4B are for the explanation of a display method in which two region has different scale map. In particular, Fig.4A is for displaying only raster type map having a scale corresponding to display scale, while Fig.4B is for displaying compound raster type maps.

To solve the second problem described above, that is in order to avoid displaying null data on the screen corresponding to the region which doesn't have the desired scale of raster type map, the largest scale of raster type map among the remnant raster type maps available each having a scale lower than the desired scale is selected to be used. For example, as shown in Fig.4B, for the KYUNGKI region not having 1/5,000 scale of raster type map, not the null data but 1/10,000 scaled raster type map is used, where the scale is the largest in the lower scales than the desired scale. By doing this, the raster type map can be effectively displayed.

Fig.5 is for the explanation of a modified raster type map display method using an upper reference value and a lower reference value and Fig.6 shows the comparison results between compound reference value type and simple reference value type.

To solve the third problem described above, one method is that different reference values are used according to the scale change direction, e.g. scale-increasing or scale-decreasing for selecting the raster type map. As shown in Fig.5, only if the designated 11 scale is increased above the reference values T.,,,p(i=l, 2, 3, 4...), the scale of raster type map is converted to the lower scale of raster type map. Also, contrary to this, only if the designated scale is decreased below the reference values T,,,,,,, (i=l, 2, 3, 4, the scale of raster type map is converted to the upper scale of raster type map. For example, if the current designated scale of raster type map is 1/10,000 scale and the display scale is increased above T1,,p by zooming-out, the current designated raster type map is replaced with a raster type map having 1/1000,000. Contrary to this, only if the display scale is decreased below T2,d,,, by zooming-in, the current raster type map is changed to the raster type map having a 1/50,000 scale.

It will be explained the replacement of raster type map in the system adopting the above reference values with reference to Fig.6. When the system uses the simple reference value T2, the time points when the raster type map to be displayed is replaced with new one are 60, 61, 62, 64, 65, 66, 68, 69. In the meantime, when the system uses the compound reference values T2,,p and T2,dw11 the replacement time points are 63 and 67.

12 is By using the compound reference values not the simple reference values, even though the display scale is frequently changed around the simple reference values as shown in Fig.5, the replacement of raster type map is seldom made so that the system speed of the system is rapidly increased.

First, the display region is initialized by reading a default region to be displayed on monitor (step 71) and the raster type map is initialized by reading a default raster type map to be displayed (step 72). Then, the default raster type map is displayed (step 73). Like this, the display area and the scale of raster type map may be handled by default values in initial stage.

Then, CPU continually checks if the display scale is changed on the screen (step 74). If the display scale is kept, the raster type map should be displayed without any change (step 73). If the display scale is changed due to zooming-in or zooming-out, the display scale to be newly displayed is determined (step 75) and the new display area is determined (step 76).

13 1 Subsequently, it is determined which ones of the reference values Ti,uP (i=l, 2, 3, 4, - -.) and Ti, down is used to select the raster type map based on scale, in order to avoid frequent-replacing the raster type map to be used according to the display scale changed due to zooming-in or zooming-out even though the display scale is slightly and frequently changed around the reference values. That is, it is determined whether the display screen is zoomed-in or zoomed-out(step 77), if the display screen is zoomed-in, the reference values Ti, d., (i=l, 2, 3, 4,...) are used to determine the scale of the city area to be displayed (step 78). On the contrary to this, if the display screen is zoomed-out, the reference values Ti,,,,, (i=l, 2, 3, 4) is used to determine the scale of the city area to be displayed (step 79). Then, the raster type map corresponding to thus-determined scale of raster type map is displayed on the screen (step 73).

Fig.8 is a detailed flowchart of the determination the scale of raster type map in zooming-in, according to the present invention.

First, Ti, d,,,, (i=l, 2, 3, 4, are used as the reference values during zooming-in operation (step 81) 14 Then, it is determined how many sheets of raster type maps are needed in order to display the designated region. This is for displaying the region not having the corresponding scale of raster type mar), using the largest scale of raster type map among the remnant lower scale ones than the designated one. That is, it is determined whether the simple raster type maps are used or the compound-raster type maps are used (step 82). If the compound raster type map is used, that is if a plural sheets of raster type maps are required, the scales of plurality of raster type maps suitable for the display scales each being newly set for respective region, are determined, respectively (step 83). On the contrary to this, the scale of the simple raster type map suitable for the display scale newly set for the corresponding region (step 84), if the simple raster type map is used, that is if only one sheet of map is needed.

Fig.9 is a detailed flowchart of the determination the scale of raster type map in zooming-out operation according to the present invention.

First, Ti, p (i=l, 2, 3, 4,...) are used as the reference values during zooming-out operation (step 91). Then, it is determined how many sheets of raster type maps 1 are needed in order to display the designated region. This is for displaying the region not having the corresponding scale of raster type map, using the largest scale of raster type map among the remnant lower scale ones than the designated one. That is, it is determined whether the simple raster type maps are used or the compound raster type maps are used (step 92). If the compound raster type map is used, that is if a plural sheets of raster type maps are required, the scales of plurality of raster type maps suitable for the display scales each being newly set for respective region, are determined, respectively (step 93). By contrast, the scale of the simple raster type map suitable for the display scale newly set for the corresponding region (step 94), if the simple raster type map is used, that is if only one sheet of map is needed.

As described above, the present invention has the following effect.

(1) The resolution of the display may be high by using the various scales of raster type map, in comparison with the conventional art in which only one scale of raster type map is used. Also, only the necessary information is displayed so that the management of memory can be 16 effectively performed and the processing speed can be increased to a considerable high degree.

(2) In case that the designated region does not have the corresponding scale of raster type map to the display scale, the largest one among the remnant lower ones than the corresponding one is used so that the raster type map can be effectively displayed.

(3) The different reference values are used according to the expansion mode or the reduction mode as references for selecting raster type maps. So, even if the display scale is frequently changed around the reference value, the replacement of raster type map being used is seldom made, to thereby increase the processing speed of system.

other various changes and modifications can be made, without departing the scope of the present invention.

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Claims

CLAIMS:

F 1 1. A raster type map display method applied to a map display apparatus, said method comprising: first step for initializing a display area and a raster type map and then displaying a raster type map having a default scale; and second step for displaying a raster type map having a scale selected among a plurality of raster type maps each having different scales, respectively, based on a display scale.
2. A method according to claim 1, wherein said second step comprising: third step for determining whether the display scale on a screen is changed or not, if the display scale is not changed, continuously displaying a raster type map currently being displayed, if the display scale is changed, newly determining a display scale and a display area and then determining whether the screen is zoomed-in or zoomedout; fourth step for determining the scale of a raster type map using a down direction reference values and then 18 displaying a raster type map corresponding to the scale of the determined raster type map, if the result of said third step is that the screen is zoomedin; and fifth step for determining the scale of a raster type map using a up direction reference values and then displaying a raster type map corresponding to the scale of the determined raster type map, if the result of said third step is that the screen is zoomed-out.

is
3. A method according to claim 2, wherein the step for determining the scale of raster type map using down direction reference values in said step 4, comprising: sixth step for making the'down direction reference values as the reference values, when zooming-in, and then determining whether a simple raster type map is used or a compound raster type map is used; seventh step for determining the scales of raster type maps according to the display scale, respectively, if the result of said sixth step represents that the compound raster type maps are used; and eighth step for determining the scale of a raster type map according to the display scale, if the result of said 19 sixth step represents that the simple raster type map is used.
4. A method according to claim 1, wherein the step for determining the scale of raster type map using up direction reference values in said fifth step, comprising: ninth step for making the up direction reference values as the reference values, when zooming-out, and then determining whether a simple raster type map is used or compound raster type maps are used; tenth step for determining the scales of raster type maps according to the display scale, respectively, if the result of said ninth step represents that the compound raster type maps are used; and eleventh step for determining the scale of a raster type map according to the display scale, if the result of said ninth step represents that the simple raster type map is used.
5. A method according to claim 2, wherein the step for determining the scale of raster type map using up direction reference values in said fifth step, comprising:

ninth step for making the up direction reference values as the reference values, when zooming-out, and then determining whether a simple raster type map is used or compound raster type maps are used; tenth step for determining the scales of raster type maps according to the display scale, respectively, if the result of said ninth step represents that the compound raster type maps are used; and eleventh step for determining the scale of a raster type map according to the display scale, if the result of said ninth step represents that the simple raster type map is used.
6. A method according to claim 3, wherein the step for determining the scale of raster type map using up direction reference values in said fifth step, comprising: ninth step for making the up direction reference values as the reference values, when zooming-out, and then determining whether a simple raster type map is used or compound raster type maps are used; tenth step for determining the scales of raster type maps according to the display scale, respectively, if the 21 result of said ninth step represents that the compound raster type maps are used; and eleventh step for determining the scale of a raster type map according to the display scale, if the result of said ninth step represents that the simple raster type map is used.

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