JP7209073B1 - Topographic map output device, topographic map output method and program - Google Patents

Abstract

A topographic map output device, a topographic map output method, and a program capable of appropriately reflecting gradients in all directions and outputting a topographic map suitable for grasping noise data are provided. A topographic map output device includes storage means for storing elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape, and for each unit area, a reference area within a predetermined reference range centered on the unit area. Detect the maximum altitude value of all unit areas included in the first range of and detect the minimum altitude value of all unit areas included in the second range within the reference range. a calculation means for calculating a combined gradient amount based on a first gradient amount between the unit area where is detected and a second gradient amount between the center area and the unit area where the minimum value is detected; and output means for outputting a topographic map displaying each unit area in a manner based on the gradient amount. [Selection drawing] Fig. 3

Description

The present invention relates to a topographic map output device, a topographic map output method and a program.

BACKGROUND ART Conventionally, a topography analysis map is used that expresses micro topography based on fine unevenness of the ground surface and altitude values relative to the surrounding topography. For example, Patent Literature 1 describes a topographic map that emphasizes unevenness due to micro-topography by using the difference between the above-ground opening and the underground opening. Patent Document 2 describes a topographic map that emphasizes unevenness due to micro-topography by using undulation feature amounts based on the elevation value of each point and the average value of the elevation values around the point.

Japanese Patent No. 3670274 Japanese Patent No. 6893307

In the topographic map described in Patent Document 1, the above-ground and underground openings at each point are calculated based only on the topography in eight directions centering on that point, so the slopes in all directions are appropriately reflected. it may not be done. In the topographic map described in Patent Document 2, since the elevation values are averaged when calculating the undulation feature amount, if local noise is included in the elevation value data, the influence of the noise is diluted and the noise is difficult to grasp, and misreading may occur. A similar problem may occur due to averaging in the topographic map described in Patent Document 1 as well. Therefore, there is a demand for a topographic map that appropriately reflects gradients in all directions and that is suitable for grasping noise data.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide a device, a topographic map output method, and a program.

A topographic map output apparatus according to the present invention comprises storage means for storing elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape, and Detect the maximum altitude value of all unit areas included in the first range of and detect the minimum altitude value of all unit areas included in the second range within the reference range. a calculation means for calculating a composite gradient amount based on a first gradient amount between the unit area where is detected and a second gradient amount between the central area and the unit area where the minimum value is detected; and output means for outputting a topographic map displaying each unit area in a manner based on the gradient amount.

Further, in the topographic map output device according to the present invention, the calculating means divides the difference obtained by subtracting the maximum value from the altitude value of the central area by the distance between the central area and the unit area showing the maximum value, and calculates the first sine is calculated as the first gradient amount, and the second sine obtained by dividing the difference obtained by subtracting the minimum value from the altitude value of the central area by the distance between the central area and the unit area showing the minimum value is calculated as the second gradient amount preferably.

Further, in the topographic map output device according to the present invention, the storage means stores a table showing the correspondence between the sine and the angle, and the calculation means calculates the difference obtained by subtracting the maximum value from the altitude value of the central area. Calculate the first sine divided by the distance between and the unit area where the maximum value is detected, and subtract the minimum value from the altitude value of the central area calculate the second sine divided by the distance between the first Preferably, the gradient amount and the second gradient amount are calculated respectively.

Further, in the topographic map output device according to the present invention, the calculation means sets a plurality of calculation ranges by expanding each unit area step by step from a size smaller than the reference range to a size equal to the reference range. Then, for each calculation range, the maximum altitude value and the minimum altitude value are detected in order, and the latter maximum value, which is the maximum altitude value in the aforementioned calculation range in the latter stage, is the altitude in the calculation range up to the previous stage. Only when it is greater than the maximum value of the previous stage, which is the maximum value of the value, the gradient amount based on the maximum value of the latter stage is calculated, and the smaller of the gradient amount based on the maximum value of the previous stage and the maximum value of the latter stage is calculated. Selected as the first slope amount, and only when the minimum value of the altitude value in the calculation range of the later stage is smaller than the minimum value of the previous stage, which is the minimum value of the altitude value in the calculation range up to the previous stage A gradient amount based on the minimum value is calculated, and the larger one of the gradient amount based on the preceding minimum value and the gradient amount based on the subsequent minimum value is selected as the second gradient amount, and the first gradient amount and the It is preferable to calculate the composite gradient amount based on the selected first gradient amount and second gradient amount when the selection of the second gradient amount is finished.

Further, in the topographic map output device according to the present invention, it is preferable that, in stepwise expanding the size of the calculation range, the calculating means increase the amount of enlargement in later stages.

Further, in the topographic map output device according to the present invention, the calculation means sets a plurality of local ranges in the target area, detects the maximum elevation value and the minimum elevation value for each of the plurality of local ranges, and The maximum value of the altitude value in the first calculation range with one unit area as the central area, and the second calculation range with the second unit area not included in the first calculation range and adjacent to the first unit area as the central area Detecting the maximum altitude value in the second calculation range based on the maximum altitude value in the included local range, the minimum altitude value in the first calculation range, and not included in the first calculation range, and It is preferable to detect the minimum altitude value in the second calculation range based on the minimum altitude value in the local range included in the second calculation range.

Further, in the topographic map output device according to the present invention, it is preferable that the calculation means calculates the composite gradient amount by adding the first gradient amount and the second gradient amount.

A topographic map output method according to the present invention is a topographic map output method executed by a topographic map output device, wherein the elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape are stored, and for each unit area , detecting the maximum value of the altitude values of all unit areas included in the first range within a predetermined reference range with the unit area as the central area, and the altitude of all the unit areas included in the second range within the reference range A first gradient amount between the central area and the unit area where the maximum value is detected, and a second gradient amount between the central area and the unit area where the minimum value is detected. calculating a synthetic gradient amount based on the synthetic gradient amount, and outputting a topographic map displaying each unit area in a manner based on the synthetic gradient amount.

A program according to the present invention is a program for a computer having a storage unit that stores elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape. Detect the maximum altitude value of all unit areas included in the first range within the reference range of , and detect the minimum altitude value of all unit areas included in the second range within the reference range. calculating a combined gradient amount based on a first gradient amount between the area and the unit area where the maximum value is detected and a second gradient amount between the center area and the unit area where the minimum value is detected; The computer is characterized by outputting a topographic map displaying each unit area in a manner based on the amount of synthetic gradient.

INDUSTRIAL APPLICABILITY A topographic map output device, a topographic map output method, and a program according to the present invention make it possible to output a topographic map that appropriately reflects gradients in all directions and that is suitable for grasping noise data.

1 is a block diagram showing a schematic configuration of a topographic map output device 1; FIG. 4 is a diagram showing the data structure of an altitude value table T1; FIG. FIG. 10 is a flowchart showing the flow of topographic map output processing; FIG. 4 is a schematic diagram for explaining the order of setting the center grid; It is a flow figure which shows the flow of a slope amount calculation process. (A) is a schematic diagram for explaining detection of maximum and minimum values in a calculation range, and (B) is a schematic diagram for explaining detection of local maximum and local minimum values in a local range. FIG. 4 is a schematic diagram for explaining calculation of a first gradient amount; (A) is an elevation gradient map of the target area, and (B) is a topographic map generated by the topographic map output device 1 for the target area. (A) and (B) are topographic maps generated by the topographic map output device 1 for the target area.

Various embodiments of the present invention will now be described with reference to the drawings. It should be noted that the scope of the present invention is not limited to those embodiments, but rather extends to the invention recited in the claims and equivalents thereof.

FIG. 1 is a block diagram showing a schematic configuration of a topographic map output device 1 according to an embodiment. A topographic map output device 1 generates and outputs a topographic map based on elevation value data such as a DEM (Digital Elevation Model). The topographic map output device 1 includes a storage unit 11 , a communication unit 12 , a display unit 13 , an operation unit 14 and a processing unit 15 . The storage unit 11 is an example of storage means.

The storage unit 11 is configured to store programs or data, and includes, for example, a semiconductor memory device. The storage unit 11 stores an operating system program, a driver program, an application program, data, and the like used for processing by the processing unit 15 . The program is installed in the storage unit 11 from a computer-readable non-temporary portable storage medium such as a CD (Compact Disc)-ROM (Read Only Memory) or a DVD (Digital Versatile Disc)-ROM.

The communication unit 12 is configured to enable the topographic map output device 1 to communicate with other devices, and includes a communication interface circuit. A communication interface circuit provided in the communication unit 12 is a communication interface circuit such as a wired LAN (Local Area Network) or a wireless LAN. The communication unit 12 receives data from another device, supplies the data to the processing unit 15, and transmits the data supplied from the processing unit 15 to the other device.

The display unit 13 is configured to display an image, and includes, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display. The display unit 13 displays images based on the display data supplied from the processing unit 15 .

The operation unit 14 is configured to receive a user's input operation to the topographic map output device 1, and includes, for example, a keypad, keyboard, or mouse. The operation unit 14 may include a touch panel integrated with the display unit 13 . The operation unit 14 generates a signal according to the user's input operation and supplies the signal to the processing unit 15 .

The processing unit 15 is a device that comprehensively controls the operation of the topographic map output device 1, and includes one or more processors and their peripheral circuits. The processing unit 15 includes, for example, a CPU (Central Processing Unit). The processing unit 15 may include a GPU (Graphics Processing Unit), DSP (Digital Signal Processor), LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), and the like. Based on the programs stored in the storage unit 11 and inputs from the communication unit 12 and the operation unit 14, the processing unit 15 controls each configuration so that various processes of the topographic map output device 1 are executed in an appropriate procedure. Controls operations and executes various processes.

The processing unit 15 includes a calculation unit 151 and an output unit 152 as its functional blocks. Each of these units is a functional module implemented by a program executed by the processing unit 15 . Each of these units may be implemented in the topographic map output device 1 as firmware. Note that the calculation unit 151 and the output unit 152 are examples of calculation means and output means.

FIG. 2 is a diagram showing an example of the data structure of the altitude value table T1 stored in the storage unit 11. As shown in FIG. The altitude value table T1 contains a plurality of rectangular geographical regions obtained by partitioning the target region displayed on the topographical map by grid-like straight lines equally spaced in the latitude and longitude directions, and the altitude value of each geographical region. Associate. In the example shown in FIG. 2, each geographic region is associated with a latitude and longitude at its central location. A rectangular geographical area is an example of a unit area and is called a grid, a cell, a mesh, or the like, but is mainly called a grid below. In other embodiments, unit areas corresponding to a plurality of geographical areas obtained by partitioning the target area into hexagonal shapes may be used. Also, the target area may be partitioned into any predetermined shape.

FIG. 3 is a flow chart showing the flow of the topographic map output process executed by the topographic map output device 1. As shown in FIG. The topographic map output process is a process of calculating a feature amount related to the gradient of each grid based on the elevation value of each grid included in the target area, and outputting a topographic map that displays each grid in a manner based on the feature amount. The topographic map output processing is realized by the processing unit 15 cooperating with each component of the topographic map output device 1 based on the program stored in the storage unit 11 .

First, the calculator 151 sets the number of grids R, which defines the size of the calculation range, to an initial value (step S11). The calculation range is an example of the first range and the second range. The calculation range is the range of grids that is referred to when calculating the feature amount of each grid, and is, for example, a square area with the grid to be calculated as the center grid. The calculation range includes from the calculation target grid to R grids in the latitudinal and longitudinal directions. That is, the width of the calculation range is (2R+1)×(2R+1).

As will be described later, the calculation range is expanded step by step from the initial value to the same width as the predetermined reference range. That is, the initial value of R is set to a small value, such as one. In this case, the initial computational range includes a 3x3 grid. Note that the calculation range is not limited to a square, and may have any shape such as a polygon or a circle. The width of the initial calculation range and the width of the reference range (that is, the upper limit of the width of the calculation range) may be stored in advance in the storage unit 11 and set by the user's input operation on the operation unit 14. may be

Next, the calculator 151 sets the center grid of the calculation range as the initial grid (step S12). The initial grid is a grid selected by the user's input operation on the operation unit 14 from among the grids included in the target area. The initial grid may be arbitrarily selected, but it is preferable to select one of the grids at the four corners of the rectangular target region because the calculation of the gradient amount calculation process, which will be described later, is made more efficient.

Next, the calculator 151 executes gradient amount calculation processing (step S13). In the gradient amount calculation process, the first gradient amount between the central grid and the grid having the maximum elevation value among the grids included in the calculation range, and the minimum elevation value among the central grid and the grids included in the calculation range is computed.

Next, the calculation unit 151 determines whether or not the gradient amount calculation process has been performed for all grids included in the target area (step S14). If the gradient amount calculation process has not been executed for all the grids (step S14-No), the calculation unit 151 sets the center grid of the calculation range to the grid next to the calculation target grid (step S14a), and step S13. proceed to That is, the calculator 151 sequentially executes the gradient amount calculation process for all grids included in the target region.

FIG. 4 is a schematic diagram for explaining the order of setting the central grid. In FIG. 4, each grid is illustrated by a circle, and each grid is arranged in a grid pattern in mutually perpendicular X and Y directions.

In the example shown in FIG. 4, the grid G[1][1], which is one of the four corner grids of the target area, is selected as the initial value of the central grid. When the gradient amount calculation process is executed for the grid G[1][1], which is the calculation target, the grid G[2][1] adjacent to the grid G[1][1] in the X direction is the next central grid. is selected as Similarly, each time the gradient amount calculation process is executed, a grid adjacent to the calculation target grid in the X direction is selected as the next center grid.

When the gradient amount calculation process is executed for the grid G[Nx][1] located at the end of the target area in the X direction, the grid G[1][2] adjacent to the grid G1 in the Y direction is the next center. selected as a grid. Thereafter, similarly, the adjacent grid in the X direction is selected as the next central grid. In this way, the grids adjacent in the X direction are sequentially selected as the next central grid, and when the grid located at the end in the X direction is selected as the central grid, the next central grid is the grid row adjacent in the Y direction. is similarly selected from Assuming that the end in the Y direction is Ny, the center grid is set in the above order until G[Nx][Ny] is reached.

The order of setting the center grids described above is an example, and the center grids may be set in any order. However, as in the above example, when a grid adjacent to the grid to be calculated in the X direction or the Y direction is selected as the next center grid, the calculation of the gradient amount calculation process is made more efficient as described later. Therefore, it is preferable. For example, when the gradient amount calculation process is executed for the grid G[Nx][1], the grid G[Nx][2] adjacent to the grid G[Nx][1] in the Y direction is the next center grid. may be selected. In this case, the grid G[Nx−1][2] adjacent to the grid G[Nx][2] in the X direction is selected as the center grid next to the grid G[Nx][2].

Returning to FIG. 3, when the gradient amount calculation process has been executed for all the grids (step S14-Yes), the calculation unit 151 determines whether the grid number R that defines the size of the calculation range is the upper limit value, That is, it is determined whether or not the calculation range is the same size as the reference range (step S15). If R is not the upper limit value (step S15-No), the calculator 151 expands the calculation range (step S15a), and proceeds to step S12. For example, the calculator 151 expands the calculation range by increasing R by a predetermined number. That is, the calculation unit 151 increases R in stages until it reaches the upper limit, and uses the calculation range of the width corresponding to each R to execute the gradient amount calculation process for each grid included in the target region. do.

If the calculation range is the same size as the reference range (step S15-Yes), the calculation unit 151 calculates the combined gradient amount of each grid based on the first gradient amount and the second gradient amount of each grid. (Step S16). For example, the calculator 151 calculates the combined gradient amount by adding the first gradient amount and the second gradient amount. The significance of the synthetic gradient amount will be described later.

Next, the output unit 152 outputs a topographic map displaying each grid in a manner based on the combined gradient amount (step S17), and terminates the topographic map output process. The aspect based on the synthetic gradient amount is, for example, brightness and hue according to the value of the synthetic gradient amount. The output unit 152 outputs the topographic map by supplying display data of the topographic map to the display unit 13 and causing the display unit 13 to display the image of the topographic map. The output unit 152 may output the topographic map by transmitting display data of the topographic map to another device via the communication unit 12 . The display data of the topographic map may be image data or data indicating the amount of synthetic gradient of each grid. As another example of a mode based on the synthetic gradient amount, the absolute value of the synthetic gradient amount is equal to or greater than a predetermined threshold value (for example, when the synthetic gradient amount is an angle as described later, 45 degrees or more or −45 degrees or less). ), it is also possible to create a topographic map in which colors are set only for unit areas. In that case, for example, the output unit 152 outputs image data of another topographical map (for example, a topographical map using the undulation feature amount of Patent Document 2) generated from the data of the altitude value table T1 and expressed in grayscale, By transmissively synthesizing and outputting topographic map image data using synthetic gradient amounts, it is possible to indicate by color unit areas where local noise may occur.

FIG. 5 is a flowchart showing the flow of gradient amount calculation processing.

First, the calculator 151 detects the maximum altitude value and the minimum altitude value among the altitude values of all grids included in the calculation range (step S21).

FIG. 6A is a schematic diagram for explaining detection of the maximum altitude value and the minimum altitude value in the calculation range. As shown in FIG. 6A, the calculation unit 151 sets a plurality of local ranges (U1, U2, U3 and U4 in the example shown in FIG. 6A) in the target region T. FIG. Each local range is set to include (2R+1) consecutive grids in the Y direction. The calculation unit 151 detects in advance the maximum elevation value and the minimum elevation value of the grid elevation values included in each local range as the local maximum value and the local minimum value, respectively.

First, the case of detecting the maximum altitude value and the minimum altitude value of the initial calculation range V1 will be described. The calculation unit 151 identifies (2R+1) local ranges (local ranges U1, U2, and U3 in the example shown in FIG. 6A) that constitute the calculation range V1. The calculation unit 151 detects the largest local maximum value of the specified local range as the maximum value of the calculation range V1. Similarly, the calculation unit 151 detects the smallest local minimum value of the specified local range as the minimum value of the calculation range V1.

Next, a case of detecting the maximum altitude value and the minimum altitude value of the calculation range V2 whose center grid is the grid adjacent to the center grid of the previous calculation range V1 will be described. In the example shown in FIG. 6A, the calculation range V2 includes local ranges U2, U3 and U4. The calculation unit 151 determines whether or not the local range indicating the local maximum value detected as the maximum value of the previous calculation range V1 is included in the calculation range V2. In the example shown in FIG. 6A, the calculation unit 151 determines that the local maximum value of the local range U1 is not detected as the maximum value of the calculation range V1 (that is, the local maximum value of the local range U2 or U3 is not detected as the maximum value of the calculation range V1). is detected as the maximum value), it is determined to be included in the calculation range V2, and if the local maximum value of the local range U1 is detected as the maximum value of the calculation range V1, it is determined not to be included in the calculation range V2. do.

When the local range where the maximum value of the calculation range V1 is detected is included in the calculation range V2, the calculation unit 151 calculates the maximum value in the calculation range V1 and the local range not included in the calculation range V1 but included in the calculation range V2. is detected as the maximum value of the calculation range V2. In the example shown in FIG. 6A, the local range U4 is a local range that is not included in the calculation range V1 but included in the calculation range V2. On the other hand, when the local range where the maximum value of the calculation range V1 is detected is not included in the calculation range V2, the calculation unit 151 calculates the local ranges U2, U3, and The largest local maximum value of U4 is detected as the maximum value of the calculation range V2.

Similarly, the calculation unit 151 determines whether or not the local range where the minimum value of the calculation range V1 is detected is included in the calculation range V2. When the local range where the minimum value of the calculation range V1 is detected is included in the calculation range V2, the calculation unit 151 calculates the minimum value of the calculation range V1 and the local range not included in the calculation range V1 but included in the calculation range V2. The smaller one of the local minimum value of U4 is detected as the minimum value of the calculation range V2. On the other hand, when the local range U in which the minimum value of the calculation range V1 is detected is not included in the calculation range V2, the calculation unit 151 calculates the local ranges U2, U3 and the local minimum value of U4 is detected as the minimum value of the calculation range V2.

Finding the maximum and minimum values in this way makes the computation more efficient. That is, when the local range where the maximum value of the calculation range V1 is detected is included in the calculation range V2, the calculation unit 151 can detect the maximum value with one comparison operation. On the other hand, if the local range where the maximum value of the calculation range V1 is detected is not included in the calculation range V2, the calculation range V2 includes (2R+1) local ranges. It takes (2R) comparison operations to detect the value. However, when adjacent grids are sequentially selected as the center grid, the calculation range slides by one grid. /(2R+1). Therefore, when the number of grids R that defines the width of the calculation range is large, the maximum value is detected in about two comparison operations on average, so the calculation is efficient. The same is true for detection of the minimum value.

FIG. 6B is a schematic diagram for explaining detection of local maximum values and local minimum values in a local range. When the center grid moves in the Y direction (in FIG. 4, G[1][2] is selected as the center grid next to G[Nx][1]), each local range is set again. , the calculation unit 151 detects the local maximum value and the local minimum value again.

In the example shown in FIG. 6B, the local range U1 in which local maxima have already been detected includes grids G1, G2 and G3, and the local range U2 includes grids G2, G3 and G4. The calculation unit 151 determines whether or not the grid of the altitude values detected as the local maximum value of the previous local range U1 is included in the local range U2. In the example shown in FIG. 6B, the calculation unit 151 determines that the elevation value of the grid G1 is not detected as the local maximum value of the local range U1 (that is, the elevation value of the grid G2 or G3 is the local maximum value of the local range U1). ), it is determined to be included in the local range U2, and if the altitude value of the grid G1 is detected as the local maximum value of the local range U1, it is determined not to be included in the local range U2.

When the grid of elevation values detected as the local maximum values of the local range U1 is included in the local range U2, the calculation unit 151 calculates the local maximum values of the local range U1 and the The larger of the included grid elevation values is detected as the local maximum of the local range U2. In the example shown in FIG. 6B, the grid G4 is a grid that is not included in the local range U1 but included in the local range U2. If the grid of the elevation values detected as the local minimum value of the local range U1 is not included in the local range U2, the calculation unit 151 calculates the largest of the elevation values of the grids G2, G3 and G4 included in the local range U2. is detected as the maximum value of the local range U2.

Similarly, the calculation unit 151 determines whether or not the grid of elevation values detected as the local minimum value of the local range U1 is included in the local range U2. When the grid of elevation values detected as the local minimum values of the local range U1 is included in the local range U2, the calculation unit 151 calculates the local minimum values of the local range U1 and the The smaller one of the elevation values of the included grid G4 is detected as the local minimum value of the local range U2. When the grid of the elevation values detected as the local minimum value of the local range U1 is not included in the local range U2, the calculation unit 151 calculates the lowest altitude value among the grids G2, G3 and G4 included in the local range U2. , is detected as the minimum of the local range U2.

Finding local maxima and minima in this way makes computation more efficient. That is, when the grid of the elevation values detected as the local maximum value of the local range U1 is included in the local range U2, the calculation unit 151 can detect the local maximum value with one comparison operation. Therefore, when the number of grids R that defines the width of the calculation range is large, the local maximum value is detected by about two comparison operations on average, and the calculation is made efficient. The same is true for finding local minima.

Returning to FIG. 5, the calculator 151 determines whether or not the first condition for calculating the first gradient amount and the second condition for calculating the second gradient amount are satisfied (step S22). The first condition is that the maximum value detected in step S21 is larger than the maximum value in the calculation range up to the previous stage (that is, the calculation range narrower than the current calculation range). The second condition is that the minimum value detected in step S11 is smaller than the minimum value in the calculation range up to the previous stage. Note that when the calculation range is the initial calculation range, both the first condition and the second condition are satisfied.

If neither the first condition nor the second condition is satisfied (step S22-No), the gradient amount calculation process ends.

If the first condition or the second condition is satisfied (step S22-Yes), the calculator 151 calculates the first condition or the second condition according to the satisfied condition (step S23). That is, the calculation unit 151 calculates the first gradient amount when the first condition is satisfied, and the calculation unit 151 calculates the second gradient amount when the second condition is satisfied.

ここで、算出範囲における最大値Ｈｍａｘは算出範囲の中心グリッドの標高値Ｈ以上であるから、第１勾配量Ｆ１は－１より大きく０以下の値をとり、－１に近いほど中心グリッドから最大値Ｈｍａｘを示すグリッドを見たときの仰角が大きいことを示す。 The first gradient amount F1 is the difference obtained by subtracting the maximum value Hmax from the altitude value H of the center grid, and the distance L between the center grid and the grid showing the maximum value Hmax (the distance L is not the horizontal distance between grids , which is a three-dimensional distance considering the difference in elevation values.). That is, the first gradient amount F1 is the negative value of the sine of the elevation angle when the grid showing the maximum value Hmax is viewed from the central grid. However, the grid showing the maximum value Hmax is the center grid, and when the distance L is 0, the first gradient amount F1 is 0. That is, the first slope amount F1 is expressed by the following equation.

Here, since the maximum value Hmax in the calculation range is equal to or higher than the altitude value H of the center grid of the calculation range, the first gradient amount F1 takes a value greater than -1 and less than or equal to 0. It indicates a large elevation angle when looking at the grid showing the value Hmax.

ここで、算出範囲における最小値Ｈｍｉｎは、算出範囲の中心グリッドの標高値Ｈ以下であるから、第２勾配量Ｆ２は、０以上であり１より小さい値をとり、１に近いほど中心グリッドから最小値Ｈｍｉｎを示すグリッドを見たときの俯角が大きいことを示す。 The second gradient amount F2 is a value obtained by dividing the difference obtained by subtracting the minimum value Hmin from the altitude value H of the center grid by the distance L between the center grid and the grid showing the minimum value Hmin. That is, the second gradient amount F2 is the sine of the depression angle when the grid showing the minimum value Hmin is viewed from the center grid. However, the grid showing the minimum value Hmin is the center grid, and when the distance L is 0, the second gradient amount F2 is 0. That is, the second slope amount F2 is represented by the following equation.

Here, since the minimum value Hmin in the calculation range is equal to or less than the altitude value H of the center grid of the calculation range, the second gradient amount F2 takes a value equal to or greater than 0 and smaller than 1. It indicates that the angle of depression is large when looking at the grid showing the minimum value Hmin.

Next, the calculation unit 151 selects the smaller one of the first gradient amount calculated in step S23 and the first gradient amount up to the previous stage as the first gradient amount in the current calculation range (step S24). Further, the calculation unit 151 selects the larger one of the second gradient amount calculated in step S23 and the second gradient amount up to the previous stage as the second gradient amount in the current calculation range (step S24 ) to end the gradient amount calculation process. That is, the first gradient amount selected in step S24 is the smallest of the first gradient amounts for the calculation range up to the current stage. Also, the second gradient amount selected in step S24 is the largest of the second gradient amounts for the calculation range up to the current stage. If the current calculation range is the initial calculation range, the gradient amount calculated in step S23 is selected as the gradient amount in the current calculation range. If the gradient amount calculated in step S23 is selected as the gradient amount in the current calculation range, the calculator 151 stores the maximum value or minimum value corresponding to the gradient amount as the current maximum value or minimum value. do.

In this way, the calculation unit 151 sets a plurality of calculation ranges of widths by gradually expanding from a width smaller than the reference range to the same width as the reference range. In step S21, the maximum and minimum altitude values are detected. Only when the maximum value in the calculation range of the subsequent stage is greater than the maximum value of the calculation range up to the previous stage, the first gradient amount is calculated in step S23. Further, only when the minimum value in the calculation range in the later stage is smaller than the minimum value in the calculation range up to the previous stage, the second gradient amount is calculated in step S23. By doing so, the calculation is made more efficient.

That is, there is a high possibility that the grid newly included in the calculation range in the later stage has a larger distance L from the central grid than the grid included in the calculation range in the previous stage. Therefore, when the maximum value in the later stage is equal to or less than the maximum value in the previous stage, the first gradient amount in the later stage is not smaller than the first gradient amount up to the previous stage (that is, the absolute value is larger), It is unlikely that the first gradient amount in the later stage will be selected in step S24. In such a case, by omitting the calculation of the first gradient amount in the later stage, the calculation becomes more efficient. Calculation of the second gradient amount is similarly made more efficient.

In step S24, the calculation unit 151 sets the smaller one of the first gradient amount based on the maximum value up to the previous stage and the first gradient amount based on the maximum value of the subsequent stage as the current stage first gradient amount. select. Further, the calculation unit 151 selects the larger one of the second gradient amount based on the minimum value up to the previous stage and the second gradient amount based on the maximum value of the subsequent stage as the second gradient amount at the current stage. By doing so, as will be described with reference to FIG. 7, a feature amount that appropriately reflects the inclination is calculated.

FIG. 7 is a schematic diagram for explaining selection of the gradient amount. In the example shown in FIG. 7, the calculation range V1 in the previous stage includes the center grid A and the grid B indicating the maximum value. In this case, the altitude value Hb of the grid B is detected as the maximum value in step S21, and the first gradient amount Fb between the grids A and B is calculated in step S23. Then, in step S24, the first gradient amount Fb is selected.

A grid C having an altitude value Hc greater than the altitude value Hb of the grid B is included in the later stage calculation range V2 with the grid A as the central grid. In this case, the altitude value Hc of the grid C is detected as the maximum value in step S21, and the first slope amount Fc between the grids A and C is calculated in step S23. However, since the upward gradient from grid A to grid C is smaller than the upward gradient toward grid B, and the first gradient amount Fc is larger than the first gradient amount Fb (that is, the absolute value is smaller), step S24 , the first gradient amount Fb is selected.

As shown in FIG. 7, the first gradient amount Fb is a feature amount corresponding to the maximum value of the elevation angle when looking from the grid A to another grid within the calculation range. That is, the first slope amount can appropriately reflect the maximum slope due to the micro-topography. In addition, since no averaging is performed for directions, the maximum slope caused by noise in local elevation values can be reflected without dilution.

If the initial calculation range is set as wide as the calculation range V2 without stepwise expansion of the calculation range, in the example shown in FIG. A first slope amount Fc corresponding to C is selected. As shown in FIG. 7, this first slope amount Fc is considered not to be a value that appropriately reflects the slope of the grid A. , the slope may not be properly reflected in the slope amount.

The slope amount is a value based not only on the elevation value of each grid but also on the distance between each grid and the center grid. Therefore, originally, even if the gradient amount is calculated only for the grid in which the maximum value or the minimum value of the altitude value is detected, it is impossible to calculate the gradient amount that appropriately reflects the inclination. However, by setting the initial calculation range narrow, the distance between each grid and the central grid becomes a close value, so the magnitude relationship of the slope amount of each grid roughly matches the magnitude relationship of the altitude value . Therefore, in the initial calculation range, if the gradient amount is calculated only for the grids in which the maximum or minimum altitude value is detected, the gradient is properly reflected in the gradient amount.

In addition, by expanding the calculation range step by step, the distances between each grid newly included in the calculation range and the center grid also become close values, so each grid newly included in the calculation range The magnitude relation of the slope amount is almost the same as the magnitude relation of the altitude value. Therefore, even in the stepwise expanded calculation range, as in the case of the initial calculation range, if the slope amount is calculated only for the grid in which the maximum or minimum value of the altitude value is detected, the slope amount will be calculated. is properly reflected.

Also, the grid from which the gradient amount is calculated is the grid in which the maximum value or the minimum value of the altitude value is detected, regardless of the orientation of the grid with respect to the central grid. Therefore, the inclination in all directions is properly reflected in the gradient amount calculated in this way. That is, the topographic map output device 1 executes the gradient amount calculation process for each calculation range while expanding the calculation range in stages, thereby making the calculations more efficient and adjusting the inclination in all directions appropriately. can be calculated.

In step S16, the composite gradient amount is calculated by adding the first gradient amount and the second gradient amount, so the composite gradient amount takes a value greater than -1 and less than 1. For example, at a point such as a valley with an upward slope in all directions, the first gradient amount indicating the upward gradient takes a value close to -1, and the second gradient amount indicating the downward gradient becomes 0. Since the values are close to each other, the combined gradient amount takes a value close to -1. At a point such as a ridge that slopes downward in all directions, the first slope value indicating the upward slope takes a value close to 0, and the second slope value indicating the downward slope takes a value close to 1. Therefore, the synthetic gradient amount takes a value close to 1. At a point where the slope is small in all directions, or at a point where there is both an upward slope and a downward slope depending on the direction, the combined slope amount takes a value close to zero. That is, the synthetic slope amount can be used as an index indicating whether the slope of the terrain is ridge-like or valley-like.

Since this combined gradient amount is calculated by adding the first gradient amount and the second gradient amount, both of which are sinusoids having a finite range, it also has a finite range. As a result, when each grid is displayed in a mode based on the synthetic gradient amount, a minute difference in the synthetic gradient amount is appropriately reflected in the display mode. That is, the topographic map output device 1 can appropriately reflect a slight inclination on the topographic map.

As described above, the topographic map output device 1 detects the maximum and minimum values of the altitude values of all grids included in the calculation range. In addition, the topographic map output device 1 outputs a first gradient amount between the central grid and the grid where the maximum value is detected, and a second gradient amount between the central area and the grid where the minimum value is detected. to calculate the synthetic gradient amount, and output a topographic map that displays each grid in a manner based on the synthetic gradient amount. As a result, the topographic map output device 1 can appropriately reflect the inclination in all directions on the topographic map.

Further, the topographic map output process does not include the process of averaging the elevation values of each grid. Therefore, even if the altitude value table T1 contains noise data in which the altitude value changes locally, the influence of such noise data is not diluted. Therefore, the topographic map output device 1 can output a topographic map that appropriately reflects gradients in all directions and is suitable for grasping noise data.

Various modifications as described below may be applied to the topographic map output device 1 .

In the above description, both the first gradient amount and the second gradient amount calculated in step S23 are assumed to be sinusoidal, but the present invention is not limited to this example. The first slope amount and the second slope amount may be angles corresponding to a sine.

In this case, in step S23, the calculation unit 151 divides the difference obtained by subtracting the maximum value Hmax from the altitude value H of the center grid by the distance L between the center grid and the grid indicating the maximum value Hmax, and calculates the first sine. calculate. Then, the calculation unit 151 calculates the arcsine (arcsin) of the first sine, that is, the first angle corresponding to the first sine as the first gradient amount. Similarly, in step S23, the calculation unit 151 divides the difference obtained by subtracting the minimum value Hmin from the altitude value H of the center grid by the distance L between the center grid and the grid indicating the minimum value Hmin, and calculates the second sine. calculate. Then, the calculation unit 151 calculates the inverse sine of the second sine, that is, the second angle corresponding to the second sine as the second gradient amount. Note that the calculator 151 may use values based on the first angle and the second angle (for example, values obtained by normalizing the first angle and the second angle) as the first gradient amount and the second gradient amount.

By doing so, various slopes can be appropriately reflected on the topographic map. That is, when the angle is close to 0 degrees, the rate of change of the sine with respect to the angle is large, but as the angle approaches ±90 degrees, the rate of change of the sine with respect to the angle becomes smaller. That is, the sine has high resolution when the angle is close to 0 degrees, but low resolution when the angle is close to ±90 degrees. On the other hand, by using the angle as the amount of slope, it is possible to prevent the resolution from being lowered even when the angle is close to ±90 degrees, and the slope of the slope close to ±90 degrees is reflected in the topographic map with high resolution. be done. However, in general, there are many terrains with inclination angles closer to 0 degrees than ±90 degrees. reflected.

In addition, when an angle is used as the gradient amount, the storage unit 11 may store a table showing the correspondence between the sine and the angle. In this case, the calculator 151 acquires the first angle corresponding to the first sine and the second angle corresponding to the second sine from the table. This reduces the calculation load of the inverse sine and makes the calculation more efficient.

In the above description, the calculator 151 calculates the first gradient amount and the second gradient amount in step S23, but instead of this, the square value of each gradient amount may be calculated. In this case, in step S16, the calculation unit 151 calculates the combined gradient amount by subtracting the square root of the square value of the first gradient amount from the square root of the square value of the second gradient amount.

In general, the latitude, longitude and altitude values of each grid are stored in the DEM as shown in the altitude value table T1. Therefore, in order to calculate the distance L from the central grid to the grid showing the maximum value or the minimum value, which is necessary for calculating the gradient amount, a square root calculation with a larger calculation load than the sum-of-products calculation is required. Since the calculation of the first gradient amount and the second gradient amount in step S23 is executed each time the first condition and the second condition are satisfied, the square root calculation is repeatedly executed, and the calculation load increases. . On the other hand, when calculating the square values of the first gradient amount and the second gradient amount, the square root operation in step S23 is not necessary, and it is sufficient to perform the square root operation once for each grid in step S16. becomes. Therefore, the calculation is made efficient.

In the above description, the calculation unit 151 expands the calculation range by increasing the number of grids R, which defines the size of the calculation range, by a predetermined number in steps S15 and S15a. can't In expanding the size of the calculation range step by step, the calculation unit 151 increases the amount of expansion (refers to the difference between R for the calculation range after expansion and R for the calculation range before expansion) at later stages. You can make it bigger. For example, the calculation unit 151 may expand the calculation range so that the size of the calculation range after expansion is a predetermined number of times the size of the calculation range before expansion. The wider the calculation range, the greater the distance L between the central grid and the grid indicating the maximum or minimum value, which is used to calculate the gradient amount. Therefore, in step S23, since there is little possibility that the gradient amount in the calculation range in the later stage is selected, even if the accuracy of the calculation is suppressed by increasing the change rate of the calculation range, errors are less likely to occur. That is, by increasing the enlargement amount in the later stages, the calculation is made more efficient while suppressing the deterioration of the calculation accuracy.

Further, the calculation unit 151 does not have to execute step S15. That is, the calculation unit 151 may execute the gradient amount calculation process using the reference range as the calculation range without setting a plurality of calculation ranges. As described above, when the calculation range is narrow, the distances between each grid and the center grid are all close values, so the gradient amount is appropriately calculated based on the maximum and minimum values. Therefore, if it is desired to reflect only the slope of the terrain in the immediate vicinity on the terrain map, it is sufficient to use only one calculation range.

In step S11, the calculation unit 151 sets the width of the calculation range to the width of the reference range, and in steps S15 and S15a, the calculation range is gradually reduced until the width of the calculation range reaches the lower limit. good too. In this case, step S22 of the gradient amount calculation process is omitted, and the calculator 151 always calculates the first gradient amount and the second gradient amount for the grid for which the maximum value or the minimum value is detected. Since steps S23 and S24 are always executed when the size of the calculation range is reduced, the amount of calculation increases compared to when the size of the calculation range is expanded, but the calculation is made more efficient to some extent. be.

In the above description, the calculation unit 151 calculates the composite gradient amount by adding the first gradient amount and the second gradient amount in step S16, but the invention is not limited to this example. The calculation unit 151 may calculate a weighted sum of the first gradient amount and the second gradient amount as the composite gradient amount. By doing so, it is possible to output a topographic map emphasizing either ridges or valleys.

An example of a topographic map output by the topographic map output device 1 will be described below.

FIG. 8(A) is an elevation gradient map of the target area, and FIGS. 8(B), 9(A) and 9(B) are topographic maps output by the topographic map output device 1 for the target area. In FIG. 8A, each grid is displayed such that the brightness increases as the altitude value increases. In addition, in FIGS. 8B, 9A, and 9B, each grid is displayed such that the brightness increases as the composite gradient amount increases. FIG. 8(B) is a diagram when the width of the reference range (that is, the upper limit of the width of the calculated range) is set to 3, and FIGS. is 21. FIG.

In FIG. 8B, since the reference range is narrow, the local tilt, that is, the step is emphasized, but the wide-range tilt is not reflected. On the other hand, in FIGS. 9A and 9B, since the reference range is wide, wide-area slopes (for example, ridges and valleys) are emphasized in addition to steps. That is, by appropriately setting the reference range, both the local slope and the wide-area slope are appropriately reflected on the topographic map.

FIG. 9A shows a case where the grid number R, which defines the width of the calculation range, is increased by 1 from 1 to 21, which is the upper limit, and FIG. 9B shows R from 1 to 8. It is a figure in the case of increasing R by 1.5 times, and then increasing R by 1.5 times. No practically problematic difference was observed between FIGS. 9(A) and (B). That is, it was confirmed that, in enlarging the calculation range, by increasing the amount of enlargement in later stages, the calculation is made more efficient without lowering the calculation accuracy.

It should be understood by those skilled in the art that various changes, substitutions and modifications can be made thereto without departing from the spirit and scope of the present invention. For example, the above-described embodiments and modifications may be combined as appropriate within the scope of the present invention.

1 topographic map output device 11 storage unit 151 calculation unit 152 output unit

Claims (9)

storage means for storing elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape;
For each unit area, the maximum value of the altitude values of all unit areas included in a first range within a predetermined reference range with the unit area as the central area is detected and included in a second range within the reference range. A first gradient amount between the central area and the unit area where the maximum value is detected, and the unit area where the central area and the minimum value are detected. a calculation means for calculating a combined gradient amount based on a second gradient amount between
output means for outputting a topographic map displaying each unit area in a manner based on the combined gradient amount;
A topographic map output device comprising: The calculation means is
calculating a first sine obtained by dividing the difference obtained by subtracting the maximum value from the altitude value of the central region by the distance between the central region and the unit region where the maximum value is detected as the first gradient amount;
A second sine obtained by dividing the difference obtained by subtracting the minimum value from the altitude value of the central region by the distance between the central region and the unit region where the minimum value is detected is calculated as the second gradient amount.
The topographic map output device according to claim 1. The storage means stores a table showing correspondence between sine and angle,
The calculation means is
calculating a first sine obtained by dividing the difference obtained by subtracting the maximum value from the altitude value of the central region by the distance between the central region and the unit region where the maximum value is detected;
calculating a second sine obtained by dividing the difference obtained by subtracting the minimum value from the altitude value of the central region by the distance between the central region and the unit region where the minimum value is detected;
obtaining from the table a first angle and a second angle corresponding to the first sine and the second sine, respectively;
calculating the first gradient amount and the second gradient amount based on the first angle and the second angle, respectively;
The topographic map output device according to claim 1. The calculation means is
Each unit area is gradually expanded from a size smaller than the reference range to the same size as the reference range to set a plurality of calculation ranges, and the maximum altitude value is set for each calculation range in sequence. and find the minimum value of the elevation value,
Slope based on the latter maximum value only when the latter maximum value, which is the maximum value of altitude values in the calculation range of the latter stage, is greater than the former maximum value, which is the maximum value of altitude values in the calculation range up to the previous stage calculating the amount, and selecting the smaller one of the gradient amount based on the preceding maximum value and the gradient amount based on the succeeding maximum value as the first gradient amount;
Slope based on the latter minimum value only when the latter minimum value, which is the minimum value of altitude values in the calculation range of the latter stage, is smaller than the preceding minimum value, which is the minimum value of altitude values in the calculation range up to the previous stage calculating the amount, and selecting the larger one of the gradient amount based on the preceding stage minimum value and the gradient amount based on the succeeding stage minimum value as the second gradient amount;
calculating the composite gradient amount based on the first gradient amount and the second gradient amount selected when the selection of the first gradient amount and the second gradient amount in each width calculation range is completed;
A topographic map output device according to any one of claims 1 to 3. The calculation means increases the amount of enlargement in a later stage in expanding the size of the calculation range step by step.
The topographic map output device according to claim 4. The calculation means is
setting a plurality of local ranges in the target region;
detecting a maximum altitude value and a minimum altitude value for each of the plurality of local ranges;
The maximum value of the altitude value in the first calculation range having the first unit area as the central area, and the second unit area having the second unit area not included in the first calculation range and adjacent to the first unit area as the central area Detecting the maximum altitude value in the second calculation range based on the maximum altitude value in the local range included in the calculation range,
Based on the minimum altitude value in the first calculation range and the minimum altitude value in a local range not included in the first calculation range and included in the second calculation range, the second calculation range find the minimum elevation value,
6. The topographic map output device according to claim 4 or 5. The calculating means calculates the composite gradient amount by adding the first gradient amount and the second gradient amount.
A topographic map output device according to any one of claims 1 to 6. A topographic map output method executed by a topographic map output device,
storing elevation values of a plurality of unit areas obtained by partitioning the target area into a predetermined shape;
For each unit area, the maximum value of the altitude values of all unit areas included in a first range within a predetermined reference range with the unit area as the central area is detected and included in a second range within the reference range. A first gradient amount between the central area and the unit area where the maximum value is detected, and the unit area where the central area and the minimum value are detected. calculating a combined gradient amount based on a second gradient amount between
outputting a topographic map displaying each unit area in a manner based on the combined gradient amount;
A topographic map output method comprising: A program for a computer having a storage unit that stores elevation values of a plurality of unit areas obtained by partitioning a target area into a predetermined shape,
For each unit area, the maximum value of the altitude values of all unit areas included in a first range within a predetermined reference range with the unit area as the central area is detected and included in a second range within the reference range. A first gradient amount between the central area and the unit area where the maximum value is detected, and the unit area where the central area and the minimum value are detected. calculating a combined gradient amount based on a second gradient amount between
outputting a topographic map displaying each unit area in a manner based on the combined gradient amount;
A program characterized by causing the computer to execute:

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