JP2007034145A - Map superimposing system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a map superimposing system that can superpose maps of various projections in real time by correcting their discrepancies. <P>SOLUTION: The vector map (basic map), based on Mercator projection method is divided into several tiles. The basic map in the tiles are formed as the basic map S1 of a predetermined size. The reference points A-D set in the basic map S1 are calculated by the Mercator method. The positions A'-D', corresponding to the longitudes and latitudes of the reference points A-D, are calculated by the UTM method on the image of the object map (aerial photograph) S2, based on the UTM method. The conversion parameters are calculated from the relations between the reference points A-D and the positions A'-D', corresponding to each other on the image on the object map S2 to superimpose the object map on the basic map. Images on the object map S2 are converted and superimposed on the basic map S1 using the calculated parameters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a system and method for overlaying different maps.

  In order to enhance the expressiveness of the map and make it easy to see the map according to the purpose, a map may be created by combining different maps. However, when overlaying different maps, in general, due to the difference in scale, accuracy, or projection method, simply aligning and overlaying the two maps will cause misalignment, resulting in a map of the desired quality. I can't.

For example, Patent Document 1 discloses a method of superimposing a map created in a predetermined coordinate system and an image in which the coordinate system is not set (such as an illustration map drawn by hand). Patent Document 2 discloses a method of superimposing topographic maps, facility maps, and the like having different scales and accuracy. Furthermore, Patent Document 3 discloses a method of combining a plurality of map images (pages) read from a map book or the like using a scanner.
JP 2002-140704 A JP 2004-101780 A JP-A-11-102156

  The methods disclosed in Patent Literatures 1 to 3 are methods for creating electronic map data suitable for overlaying a specific map, or pasting a large number of maps using various scales and projection methods. This method discloses a method for creating a single wide-area electronic map data by combining them, and it is necessary for an operator to manually perform an operation for correcting a shift.

  On the other hand, today, it is conceivable to display a synthesized image while executing superposition of maps by appropriately using electronic map data created based on various projection methods. In such a system, it is necessary to automatically perform superposition at a speed that does not hinder scrolling. However, Patent Documents 1 to 3 do not assume that different maps are superimposed and displayed in real time while correcting the shift.

  An object of the present invention is to provide a map overlay system and a method for superimposing maps in real time while correcting a shift between maps having different projection methods. In particular, an object of the present invention is to provide a map overlay system and method capable of simultaneously executing scrolling and overlay processing.

  A map superposition system according to the present invention is a map superposition system that superimposes a basic map created based on a first projection method and a target map created based on a second projection method. Is divided into a plurality of tile areas, and the basic map and the target map are overlaid in units of tile areas.

  The map superposition system further includes basic map drawing means for drawing a basic map of a tile area as a basic map tile image of a predetermined image size, and first and second longitudes and latitudes of two or more reference points set in the basic map tile image. Longitude and latitude calculating means for calculating based on the projection method, image position calculating means for calculating the position on the target map image corresponding to the longitude and latitude of the reference point based on the second projection method, and on the basic map tile image Conversion parameter calculation means for calculating a parameter of a conversion formula for superimposing the image of the target map on the basic map tile image from the relationship between the position of the reference point and the position on the image of the target map corresponding to the reference point; Synthesis means for converting the image of the target map based on the parameters and superimposing the image on the basic map tile image.

  For example, the basic map is a vector map, and the target map is a raster map. The predetermined image size is smaller than the image display area for displaying the basic map and the target map. Further, the map overlay system includes data acquisition means for acquiring a plurality of basic map tile images necessary for filling up the image display area and images of the target map corresponding thereto.

  The map overlay system preferably includes means for storing in the cache memory the composite image generated by the compositing means for each tile area. The map overlay system further includes scroll means for scrolling the composite image displayed in the image display area, and the scroll means is only scrolled when exceeding the range of the composite image stored in the cache memory, for example. A composite image of the basic map tile image not stored in the cache memory and the image of the target map corresponding to the basic map tile image is created. Further, the data acquisition means rearranges a list of tile areas necessary to fill the image display area in order from the center of the image display area. Further, the conversion formula is, for example, linear conversion.

  A map overlay method according to the present invention is characterized by using the map overlay system.

  As described above, according to the present invention, it is possible to provide a map overlay system and a method for superimposing maps in real time while correcting a shift between maps having different projection methods. It is possible to provide a map overlay system and method capable of simultaneously executing scrolling and overlay processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram schematically showing the configuration of a map overlay system that is one embodiment of the present invention.

  The map superposition system shown in FIG. 1 illustrates the case where one independent computer 10 is used. The computer 10 is, for example, a normal personal computer system, and a display 14, a main memory 16, a hard disk 18, and an input device 20 are connected to the CPU 12 via a bus (internal bus, memory bus, etc.) BS. Further, a cache memory 22 is connected to the CPU 12. In the figure, components that are not used in the map superposition system are omitted.

  The hard disk 18 stores a map overlay system program (map synthesis program) P and electronic map data used in the map synthesis program P. As electronic map data, basic map data D0 and target map data D1 are stored as independent files, for example. The basic map data D0 is vector map data, and the target map data D1 is, for example, raster map data. Examples of the raster map include a raster map based on an aerial photograph (aerial photograph, satellite photograph, etc.), a normal topographic map, and a road map. A vector map can be used as the target map, and a raster map can be used as the basic map. A plurality of basic map data D0 and target map data D1 may exist, and in this case, map data used by the user is appropriately selected.

  In this specification, the basic map is a map that is used as a reference in the map superimposition process, and the target map is a map on which the basic map is superimposed. The projection method generally used is different between the basic map and the target map. For example, Mercator projection is used for vector maps, and Universal Transverse Mercator (UTM) projection is used for aerial photographs. Therefore, in the superimposition process between the basic map and the target map, simply performing enlargement / reduction based on the position alignment or the difference in scale causes a deviation in superimposition. These deviations are particularly large when the overlay process is applied to the entire wide area. For example, when a map based on the Mercator projection and a map based on the UTM projection are overlapped with the latitude and longitude of the center aligned, the deviation increases as the distance from the center increases.

  In the present invention, the difference in projection method between the basic map and the target map is absorbed by a method with a small calculation load, and the basic map data D0 and the target map data D1 created based on different projection methods are directly used. While being used, it is possible to execute superposition in real time in an interactive operation. At the same time, the map can be scrolled at high speed. Note that the map overlay system of this embodiment can be applied as it is even when the projection method of the basic map and the target map is the same.

  Next, with reference to FIG. 2 and FIG. 3, the basic concept of the map overlay processing of this embodiment will be described.

  The basic map data D0 and the target map data D1 are, for example, map data that covers the whole of Japan. As shown in FIG. 2, in the map superimposition processing of this embodiment, the entire basic map is divided into a large number of rectangular areas (tiles) arranged in a grid pattern, and map superimposition is performed in units of these tiles. Processing is executed. FIG. 2 schematically shows a state where the whole of Japan is covered with a large number of tiles, with the upper left corner of the tile (0, 0) being the origin (for example, a point in Gifu Prefecture). In FIG. 2, a frame F exemplifies the range of the map displayed on the display 14 (see FIG. 1). In general, map data is stored in a file in units of rectangular areas, but the size of tiles for which map overlay processing is executed and the size of the rectangular area of the map data file do not have to be the same. The method that draws a part of the stored area from the map data of one file or reads the data from multiple files and draws it into one image is already commonly used. It has been.

  As for the size of the tile, the deviation due to the projection method between the basic map and the target map in each tile is simple, such as affine transformation, secondary conformal transformation, bilinear transformation, cubic equiangular transformation, projective transformation, etc. It is set to a sufficiently modifiable range within an allowable range by simple conversion. For the display 14, for example, when the map display area on the display 14 is 1280 × 1024 pixels, the tile is set to a predetermined image (memory) size smaller than this, for example, 256 × 256 pixels. This is a setting for smoothly performing a scroll process described later.

  FIG. 3 is a diagram schematically illustrating a method of superimposing processing between the basic map and the target map in each tile.

  The basic map S1 shown in FIG. 3 is a map of the area corresponding to the tile in the basic map data D0. The size of the tile with respect to the basic map is determined by the user specifying the scale scale of the map. That is, the map data is created for each predetermined scale layer and holds data according to the scale layer. In each scale layer, an appropriate size relationship between the basic map and the tile is set in advance, and when the scale layer is specified, the vector with the above set value corresponds to the size of the tile on the screen. Data is developed based on, for example, Mercator projection. Note that the scale hierarchy for the basic map may be set to a predetermined value by default.

  On the other hand, since the target map is created by a projection method different from that of the basic map, the map of the same area as the basic map S1 is read from the target map data D1 as it is and the center of the map is aligned and displayed. As described above, a deviation occurs from the basic map S1. In addition, a deviation may occur due to a slight difference in scale between the basic map and the target map. In order to correct such a shift, at least two or more corresponding reference points are set for each of the basic map and the target map in each tile, and a conversion parameter for adapting the target map to the basic map is calculated for each tile. Is done. Here, the conversion parameter is a parameter used in a conversion formula (affine transformation, secondary equiangular transformation, bilinear transformation, cubic equiangular transformation, projective transformation, etc.) used when the target map is adapted to the basic map. The number of parameters and the number of reference points are determined in accordance with the conversion formula employed.

  In the present embodiment, for example, a simple linear transformation with the tile center as the origin, which only scales the target map (the origin may be, for example, one of the four corners of the tile, and is not limited to the tile center). ) Will be described as an example. As shown in FIG. 3, as reference points, for example, four points (midpoints of each side) A, B, C, and D at positions corresponding to both ends of a tile on a horizontal and vertical line passing through the tile center of the basic map are (If it is possible to cope with isotropic scaling, only one of the points A and B or the points C and D may be used). Note that the position of the reference point is arbitrary, and may be, for example, the four corners of the tile or a point in the tile.

  First, the longitude and latitude are obtained from the pixel coordinates of the reference points A, B, C, and D set on the tile of the basic map S1 based on the Mercator projection, and the reference points A ′ and B ′ in the target map corresponding to the longitude and latitude are obtained. , C ′, D ′ pixel coordinates are determined using the UTM projection used to create the target map. Next, the horizontal enlargement ratio α is determined from the ratio of the number of pixels between AB and the number of pixels between A′B ′, and the vertical expansion is determined from the ratio of the number of pixels between CD and the number of pixels between C′D ′. The rate β is determined. Then, based on the enlargement rates α and β, the target map S2 is scaled in the horizontal and vertical directions and superimposed on the basic map S1 (FIG. 3 illustrates the case where the target map is enlarged).

  Note that, as described above, the size of the tile is set so as to be within the allowable error range under the conversion in which the deviation due to the difference in the projection method is used, so the target map is a map based on the UTM projection. Even if it exists, the target map can be superimposed on the basic map with sufficient accuracy. Further, when the target map is enlarged, an interpolation process is executed, and when the target map is reduced, a thinning process is executed.

  As described above, according to the present embodiment, maps are overlapped in units of tiles having a size capable of absorbing a shift due to a difference in projection method between the maps to be overlaid. Can be realized, and maps can be superimposed in real time.

  Next, with reference to FIG. 1 and FIG. 4, scroll processing in the present embodiment will be described. FIG. 4 is a schematic diagram showing the relationship between the screen frame F and the tiles constituting the entire map. The scroll operation is expressed as the screen frame F moving with the tile position fixed.

  When the screen frame F is initially at the position of the frame p1, the basic map data D0 and the target map data D1 of the area corresponding to the 25 tiles with colors including the frame p1 are transferred from the hard disk 18 to the main memory 16. It is read out, subjected to the above superposition process, displayed on the display 14 as a composite map, and stored in the cache memory 22. That is, when the user scrolls the screen frame F within the range stored in the cache memory 22 by using a mouse or a keyboard which is one of the input devices 20, new data is read or superimposed. Without scrolling, the map is scrolled and displayed on the display 14.

  On the other hand, when the screen frame F is scrolled to the frame p2 beyond the cached range, only the map data corresponding to the tiles not stored in the cache memory 22 is read from the hard disk 18 and the overlay process is performed. This is executed and displayed on the display 14, and data in this area is newly stored in the cache memory 20. At this time, unnecessary data is erased from the cache memory. In FIG. 4, only tiles in the minimum area including the screen frame F are shown as being stored in the cache memory 20, but tiles in a wider area can be stored in the cache memory 20. .

  As described above, by setting the size of the tile on the screen to be smaller than the display screen frame, when scrolling beyond the area stored in the cache memory, it is newly read and the overlay process is performed. Since the amount of data to be reduced can be reduced, smoother scrolling can be realized.

  Next, with reference to FIG. 5, the processing procedure of the entire map overlay system of this embodiment will be described. FIG. 5 is a flowchart showing a processing procedure of the entire map overlaying system of this embodiment.

  The basic map and the target map are selected by the user. For example, the tile displayed at the center of the screen is determined by designating the longitude and latitude or the address, postal code, telephone number, etc., and the scale hierarchy of the displayed map is When selected by the user, the drawing process of the present embodiment is started (the longitude and latitude and the scale layer that are the center may be given by default). At this time, the user can select an item to be drawn as a map from the basic map data D0 that is a vector map. That is, in the basic map data D0, data is stored for each item, such as roads, railways, subways, and notes, and the user can select items to be displayed on the map.

  In step S100, a list of tiles necessary to fill the display screen (screen frame F) is acquired. In step S102, the center positions of the tiles in the acquired list are rearranged in order from the center of the screen. . In addition, when there are a plurality of tiles having the same distance, they may be arranged in an arbitrary order, but may be given regularity such as rearranging in order clockwise from the upper left. In step S104, one tile is sequentially selected from the list of tiles rearranged in step S102 according to the rearrangement order. In step S106, it is determined whether or not the selected tile already exists in the cache list (the list of tiles stored in the cache memory 20).

  If the selected tile does not exist in the cache list, the process proceeds to step S108, and the data corresponding to the tile is read from the basic map data D0 and the target map data D1 of the hard disk 18, and the above overlay processing is performed. The created image data is created. In step S110, the image data of the tile created in step S108 is stored in the cache memory 20 and the tile is added to the cache list. Further, the image data of the tile stored in the cache memory 20 is transferred to the display 14 in step S112 and rendered on the screen.

  On the other hand, if it is determined in step S106 that the selected tile exists in the cache list, the process directly proceeds to step S112. That is, the image data corresponding to the tile is read from the cache memory 20 and drawn on the display 14.

  In step S114, it is determined whether all tiles listed in the list of tiles that fill the display screen have been drawn. When all the tiles in the tile list are not drawn, the process returns to step S104, the next tile is selected based on the above order, and the processes in and after step S106 are repeated for the tile. If it is determined in step S114 that all tiles in the tile list have already been drawn, this drawing process ends. The drawing process is repeatedly executed while the position of the tile with respect to the screen is gradually moved even when scrolling is performed.

  Next, the map drawing process on the tile in step S108 of FIG. 5 will be described with reference to FIGS. As shown in the flowchart of FIG. 6, the map drawing process on the tile in step S108 mainly includes the processes of step S200 and step S202. In step S200, the basic map is drawn on the tile, and step S202 is performed. Then, drawing on the tile of the target map is performed.

  The contents of the basic map drawing process in step S200 are shown in the flowchart of FIG. In the basic map drawing process (step S200), first, in step S300, the vector data of the area corresponding to the tile is retrieved from the basic map data D0 of the hard disk 18. Thereafter, in step S302, the retrieved vector data is read and a vector map is drawn, and the basic map drawing process ends.

  Next, the drawing process of the target map in step S202 of FIG. 6 will be described with reference to the flowchart of FIG. In the target map drawing process (S202), raster data of the area corresponding to the tile is searched from the target map data D1 of the hard disk 18 in step S400. Next, in step S402, enlargement ratios (horizontal and vertical enlargement ratios α, β) of the target map with respect to the basic map at the center position of the tile are calculated. In step S404, the target map composed of raster data corresponding to the tile is enlarged at the enlargement ratio, and is overlaid on the basic map (vector map) drawn on the tile in step S200. Thus, the drawing process of the target map (S202) is completed, and the map drawing process (S108) on the tile is thereby completed.

  The process for determining the magnification in step S402 will be described with reference to the flowchart of FIG. In step S500, the expansion rate of the linear transformation of the target map with the tile center as the origin is obtained for each tile. As described with reference to FIG. 3, the pixel coordinates of the midpoint A and the midpoint B of the left side of the tile are converted into longitude and latitude using the projection method (Mercatl projection) on the basic map (this In the flowchart, the case where only the enlargement ratio α is obtained will be described as an example). In step S502, using the projection method (UTM projection) on the target map, the latitudes and longitudes of the reference points A and B are converted into the pixel coordinates of the tiles of the target map to obtain corresponding reference points A 'and B'. In step S504, the magnification α is obtained from the number of pixels between AB (pixel distance) that is the width of the tile and the number of pixels between A′B ′ (pixel distance) on the target map, and this magnification is determined. This process ends.

  As described above, according to the map overlay system of the present embodiment, in overlaying maps with different projection methods, the entire map is considered to be a combination of many tiles, and the map overlay process is performed using tiles. By using the unit, it is possible to correct the deviation at a very high speed. As a result, the maps can be superimposed in real time. Further, by setting the size of the tile on the screen to be smaller than the image display area, the map can be scrolled at high speed.

  Note that in addition to the configuration described so far, a function for changing the transparency of the vector map may be added to improve the expressive power by combining the vector map and a raster map such as an aerial photograph.

  In the present embodiment, a stand-alone computer is assumed, and basic map data and target map data are stored in a hard disk connected to the computer. However, the map overlay system uses an electronic map via a network such as the Internet or a LAN. Data (basic map data, target map data) may be used. In this case, the electronic map data is recorded on a recording medium such as a hard disk on the server side. In addition to the hard disk, various media such as CD, MO, DVD, and IC memory can be used as the recording medium for recording the electronic map data.

  In the present embodiment, the Mercator projection and the universal horizontal Mercator projection are given as examples of the projection method of the basic map and the target map. However, the projection method of each map is not limited to these combinations, and various known methods The present invention can be applied to a projection method.

It is a block diagram which shows typically the structure of the map superposition system which is one Embodiment of this invention. It is a figure which represents typically that the whole map is comprised from many tiles arranged in the grid | lattice form. It is a figure which shows typically the method of the superimposition process between the basic map and object map in each tile. It is the model which showed the relationship between the screen frame and the tile which comprises the whole map, and represents scroll operation as a screen frame moving, fixing the position of a tile. It is a flowchart which shows the process sequence of the whole map superimposition system of this embodiment. It is a flowchart of the map drawing process to the tile performed in step S108 shown by FIG. 7 is a flowchart of basic map drawing processing executed in step S200 shown in FIG. 6. It is a flowchart of the drawing process of the object map performed in step S202 of FIG. It is a flowchart of the process for determining the magnification performed in step S402 of FIG.

Explanation of symbols

10 Map superposition system 12 CPU
14 Display 16 Main memory 18 Hard disk 22 Cache memory A, B, C, D Reference point D0 Basic map data D1 Target map data F Screen frame S1 Basic map S2 Target map

Claims (10)

A map superposition system that superimposes a basic map created based on a first projection and a target map created based on a second projection,
A map superposition system, wherein the basic map is divided into a plurality of tile areas, and the basic map and the target map are overlaid in units of the tile areas. Basic map drawing means for drawing the basic map of the tile area as a basic map tile image of a predetermined image size;
Longitude and latitude calculating means for calculating longitude and latitude of two or more reference points set in the basic map tile image based on the first projection method;
Image position calculating means for calculating a position on the image of the target map corresponding to the longitude and latitude of the reference point based on the second projection method;
A conversion formula for superimposing the target map image on the basic map tile image based on the relationship between the position of the reference point on the basic map tile image and the position on the target map image corresponding to the reference point. Conversion parameter calculation means for calculating the parameters of
The map overlay system according to claim 1, further comprising: a combining unit that converts an image of the target map based on the parameter and overlays the image on the basic map tile image.   The map overlay system according to claim 2, wherein the basic map is a vector map, and the target map is a raster map.   The map overlay system according to claim 2, wherein the predetermined image size is smaller than an image display area for displaying the basic map and the target map.   5. The map superposition system according to claim 4, further comprising data acquisition means for acquiring a plurality of the basic map tile images necessary for filling the image display area and images of a target map corresponding thereto. .   6. The map superposition system according to claim 5, further comprising means for storing, in a cache memory, a synthesized image generated by the synthesizing means for each tile area.   Scroll means for scrolling the composite image displayed in the image display area is stored in the cache memory only when scrolling is performed beyond the range of the composite image stored in the cache memory. 7. The map superposition system according to claim 6, wherein a composite image of a basic map tile image that has not been performed and an image of a target map corresponding thereto is created.   6. The data acquisition unit according to claim 5, wherein a list of tile areas necessary to fill the image display area is rearranged in order of distance from the center of the image display area to the center of the tile area. The map overlay system described in 1.   The map superposition system according to claim 2, wherein the conversion formula is linear conversion.   A map overlaying method using the map overlaying system according to any one of claims 1 to 9.

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