Surface water flow display system

Abstract

It is an object of the present invention to solve the problems of the prior art, i.e. to provide a surface water flow display system which can display the flow of surface water more easily than the prior art.SOLUTION: This surface water flow display system is a system for displaying the flow of surface water by using topographic map data set in a plane coordinate system and a plurality of meshes set in the topographic map data, and is provided with an initial point display means, a moving vector setting means and a moving point display means. A moving direction is set for each mesh. The moving point display means displays a new moving point at a position to which the moving point moves by the moving vector related to the mesh including the latest moving point every time the moving time elapses.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to technology related to water flowing on the surface of the earth, such as in streams and rivers (hereinafter referred to as "surface water"), and more specifically to a surface water flow display system that allows users to intuitively grasp the flow of surface water. [Background technology]

[0002] The 21st century has been called the "century of water," and in recent years, there has been growing social interest in water as a resource and the water cycle. Against this background, the Basic Act on Water Cycle came into effect in July 2014, and the Basic Plan for Water Cycle to put the Basic Act on Water Cycle into practice was approved by the Cabinet in July 2015. The Basic Act on Water Cycle aims to promote water cycle measures in a comprehensive and integrated manner, and to maintain or restore a healthy water cycle, thereby promoting the sound development of the economy and society and improving the safety of people's lives. It is based on five basic principles: the importance of the water cycle, the public nature of water, consideration for a healthy water cycle, comprehensive management of river basins, and international cooperation on the water cycle.

[0003] Here, the water cycle is defined as "the circulation of water as surface water or groundwater around river basins, as it evaporates, descends, flows down, or seeps into the sea or other areas." Along with groundwater flow, the flow of surface water, such as streams and rivers, is also considered important. Naturally, surface water flows from higher to lower elevations, so a topographical map showing contour lines can help visualize the general flow of surface water. However, "reading" surface water flow based on contour lines requires considerable specialized knowledge and experience with topographical maps, making it difficult to demonstrate surface water flow to the average person. While there have been examples of using animation (frame-by-frame) to illustrate surface water flow, these methods were expensive to produce and did not lead to sufficient understanding.

[0004] There is a strong demand for easy-to-understand displays of water flow, and various technologies have been proposed to meet this demand. For example, Patent Document 1 proposes a technology for creating "flow lines" that represent groundwater flow based on the results of a separate simulation, and for displaying flow lines related to multiple points. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-77282 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention disclosed in Patent Document 1 makes it possible to display groundwater flow, which is normally invisible to the naked eye, and furthermore, to express the movement of groundwater over time, allowing for an intuitive understanding of groundwater flow. Furthermore, since it can be viewed by many stakeholders at the same time, it can be extremely useful when taking measures when a problem occurs. Meanwhile, no effective technology has been proposed for displaying the flow of surface water in an easy-to-understand manner.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, that is, to provide a surface water flow display system that can display surface water flow more easily than the prior art. [Means for solving the problem]

[0008] The present invention focuses on the use of topographic map data provided by the Geospatial Information Authority of Japan and mesh data with three-dimensional coordinates to display the flow of surface water according to the direction of movement set for each mesh, and is an invention based on an idea that has not been seen before.

[0009] The surface water flow display system of the present invention displays the flow of surface water using "topographic map data" set in a plane coordinate system and multiple "meshes" set within the entire (or partial) range of the topographic map data, and is equipped with an initial point display means, a movement vector setting means, and a moving point display means. Each mesh has three-dimensional coordinates, and a movement direction is set based on the surrounding meshes. The initial point display means displays an initial point at one or more predetermined (or operator-specified) positions in the topographic map data. The movement vector setting means sets a movement vector based on the movement direction and movement distance (the product of a predetermined movement speed and movement time). The moving point display means displays a moving point at a position where the initial point has moved by the movement vector related to the mesh including the initial point when movement time has elapsed since the initial point was displayed. The moving point display means then displays a new moving point at a position where the moving point has moved by the movement vector related to the mesh including the latest moving point each time movement time has elapsed.

[0010] The surface water flow display system of the present invention can also be configured to end the display of the initial point when a predetermined display period has elapsed after displaying the initial point, and to end the display of the moving point when a display period has elapsed after displaying the moving point.

[0011] The surface water flow display system of the present invention can also be configured to change the shade of the display color of the initial point as time passes after the initial point is displayed, and to change the shade of the display color of the moving point as time passes after the moving point is displayed.

[0012] The surface water current display system of the present invention may further comprise a display condition setting means for setting the moving speed and moving time by an operator. The moving speed and moving time can be dynamically changed by using the display condition setting means even while the moving point is being displayed by the moving point display means.

[0013] The surface water flow display system of the present invention can also be configured to set a movement speed according to the terrain gradient. In this case, the terrain gradient of each mesh is calculated based on the three-dimensional coordinates of that mesh and its surrounding meshes, and a speed coefficient according to the terrain gradient is set. The movement speed for each mesh is then set as a value obtained by multiplying a preset movement speed by the speed coefficient for the mesh.

[0014] The surface water flow display system of the present invention can also be configured to set a movement speed according to a speed coefficient. In this case, a speed coefficient according to the type of feature associated with each mesh is set, and the movement speed associated with each mesh is set as a value obtained by multiplying a preset movement speed by the speed coefficient associated with that mesh. [Effects of the Invention]

[0015] The surface water flow display system of the present invention has the following advantages. (1) The flow of surface water can be intuitively confirmed, and therefore information about surface water can be shared among many people. (2) For example, by sharing information on the flow of surface water through various councils, it is possible to identify issues with the water cycle in the area and take effective measures to address them. (3) Even those who cannot judge from contour lines can easily and intuitively grasp the flow of surface water. As a result, it is expected that more people will become interested in water as a resource and in the water cycle, and that this will lead to a growing momentum in society. [Brief explanation of the drawings]

[0016] [Figure 1] 1A is an image showing the flow of surface water displayed by the surface water flow display system of the present invention, and FIG. 1B is an image showing an example of a display condition setting means constituting the surface water flow display system of the present invention. [Figure 2] 1 is a block diagram showing the main configuration of a surface water flow display system according to the present invention; [Figure 3] A model diagram showing the "movement direction" set for each mesh. [Figure 4] A model diagram showing a method for calculating movement direction based on the rate of change of elevation, which consists of two components on the X and Y axes. [Figure 5] FIG. 1 is a flowchart showing an example of the main processing flow of a surface water flow display system. [Figure 6] FIG. 1 is a step diagram illustrating the process by which the surface water flow display system displays the surface water flow. DETAILED DESCRIPTION OF THE INVENTION

[0017] An example of an embodiment of the surface water flow display system of the present invention will be described with reference to the drawings.

[0018] FIG. 1(a) is an image diagram showing the flow of surface water displayed by the surface water flow display system of the present invention. As shown in this figure, the surface water flow display system of the present invention displays the flow of surface water and is a viewer that allows even those without specialized knowledge to intuitively understand the flow of surface water. Specifically, one or more points (hereinafter referred to as "initial points") are displayed at a predetermined position, and then another point (hereinafter referred to as "moving points") is displayed at a position where the initial point is estimated to move. After displaying a moving point, another moving point is displayed at a position where the moving point is estimated to move, and this process is repeated to display multiple moving points. By displaying multiple moving points at extremely short distance intervals and increasing the number of moving points displayed over time, the flow of surface water can be expressed. For convenience, the initial point and moving points will be collectively referred to as "display points."

[0019] 2 is a block diagram showing the main components of the surface water current display system 100 of the present invention. As shown in this figure, the surface water current display system 100 includes an initial point display means 101, a movement vector setting means 102, and a movement point display means 103, and can also include a display condition setting means 104, a topographical map data storage means 105, a 3D topographical model storage means 106, a display condition storage means 107, etc.

[0020] The initial point display means 101, movement vector setting means 102, movement point display means 103, and display condition setting means 104 that make up the surface water flow display system 100 can be manufactured as dedicated devices, or a general-purpose computer device can be used. That is, the processing of the various means is performed by having the computer device execute calculations using a predetermined program. This computer device is equipped with a processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), memories such as ROM and RAM, and some also include input means such as a mouse and keyboard, and a display, and can be configured, for example, as a personal computer (PC) or server.

[0021] The topographical map data storage means 105, the 3D topographical model storage means 106, and the display condition storage means 107 can be configured as a storage device of a general-purpose computer (for example, a personal computer), or can be configured as a database server. When configured as a database server, they can be placed on a local network (LAN: Local Area Network), or can be configured as a cloud server that stores data via the Internet.

[0022] Below, each of the main elements that make up the surface water flow display system 100 will be described in detail.

[0023] (Topographical map data storage means) The topographical map data storage means 105 stores "topographical map data" set in a planar coordinate system. Here, a planar coordinate system is a coordinate system on a horizontal plane represented by latitude and longitude, or X-axis and Y-axis. The surface water flow display system 100 can use various types of topographical map data that have been used conventionally as long as the topographical map is set in a planar coordinate system, and can use topographical map data provided by the Geospatial Information Authority of Japan, for example. Although it has been described as "set in a planar coordinate system," it is of course also possible to use three-dimensional "topographical map data" that includes height information (elevation) in addition to planar coordinates.

[0024] (3D terrain model storage means) The 3D terrain model storage means 106 stores a "3D terrain model." A 3D terrain model is a three-dimensional representation of terrain based on multiple 3D coordinates (3D point clouds), and typical examples include a "digital surface model (DSM)" and a "digital elevation model (DEM)." A 3D terrain model is formed by dividing the planar range of the target terrain into multiple small areas (hereinafter referred to as "meshes") and assigning heights to representative points of each mesh. Methods for assigning heights to representative points of meshes include the triangulated irregular network (TIN) method, which calculates heights using an irregular triangulation network formed from random data; the nearest neighbor method, which uses the nearest measurement point; the inverse distance weighting (IDW) method; the Kriging method; and the averaging method.

[0025] The multiple meshes that make up the 3D topographical model are set within all or part of the planar range of the topographical map data. In other words, when the topographical map data and the 3D topographical model are viewed in plan, they either completely match, or the 3D topographical model is included in the topographical map data. The topographical map data storage means 105 of the present invention then performs various processes on the multiple meshes included within the range of the topographical map data.

[0026] As shown in FIG. 3, each of the meshes MS constituting the 3D terrain model is assigned a "movement direction MD," and the 3D terrain model storage means 106 associates and stores the meshes MS with the movement direction MD. Here, the movement direction MD is the direction in which surface water is expected to move once it reaches that mesh MS. Because surface water moves from higher to lower elevations, the movement direction MD can be set based on the elevation of the surrounding meshes MS, and can be set using various conventional methods. For example, FIG. 4 shows a method for calculating the movement direction MD based on the rate of change of elevation, which is composed of two components, the X-axis (east-west direction) and the Y-axis (north-south direction). An example of a procedure for calculating the movement direction MD will be described below with reference to FIG. 4.

[0027] First, for the target meshes MS, the X-axis is set so that east is positive (+), and the Y-axis is set so that north is positive (+). Next, the elevations Za to Zh of the eight meshes MSa to MSh adjacent to the target mesh MS0 are read from the 3D terrain model storage means 106. Then, the elevation change rate in the X-axis direction (hereinafter simply referred to as the "X-direction change rate DZx") is calculated according to equation (1), and the elevation change rate in the Y-axis direction (hereinafter simply referred to as the "Y-direction change rate DZy") is calculated according to equation (3). The horizontal load coefficient values ​​W1 to W4 (so-called "weights") included in equations (1) and (3) can be calculated as shown in equations (2a) to (2c). Once the two components, the rate of change DZx in the X direction and the rate of change DZy in the Y direction, are obtained, the movement direction MDr in radians can be calculated using their arctangent function, i.e., equation (4a), and the movement direction MDd in degrees can be calculated using equation (4b).

[0028] (Display condition setting means) As described above, the surface water flow display system 100 represents the flow of surface water by displaying new moving points at positions where it is estimated that a display point (initial point or moving point) will subsequently move. A new moving point is additionally displayed each time a predetermined time (hereinafter referred to as "moving time") has passed, and is displayed at a planar position calculated based on a predetermined speed (hereinafter referred to as "moving speed"). Furthermore, once a predetermined time (hereinafter referred to as "display period") has passed after a display point is displayed, the display can be terminated (i.e., disappeared).

[0029] The display condition setting means 104 is a means for setting conditions for displaying surface water flow (hereinafter simply referred to as "display conditions"). These display conditions can include, in addition to the moving speed, moving velocity, and display period, the "number of display points," "display color," "dimension (diameter) of the display points," and "shade of the display points," as shown in FIG. 1(b). The display conditions are set by an operator operating the display condition setting means 104. For example, in FIG. 1(b), the display conditions displayed as a bar are set (changed) using a pointing device (mouse, touch panel, pen tablet, touchpad, trackpad, trackball, etc.) or a keyboard. The display conditions can be set using the display condition setting means 104 before the display points are displayed, or they can be changed while the display points are being displayed. The surface water flow display system 100 can also be configured without the display condition setting means 104, without changing the default display conditions. The display conditions set using the display condition setting means 104 are stored in the display condition storage means 107 (FIG. 2).

[0030] The travel speed set by the display condition setting means 104 (or the default travel speed) is basically assigned to all mesh MSs. However, depending on the attributes of the mesh MSs, it may not be appropriate to treat them as the same travel speed. Therefore, a travel speed can be set according to the attributes of the mesh MSs. In this case, a travel speed according to the attributes can be set from the beginning, or a travel speed independent of the attributes (hereinafter referred to as the "reference travel speed") can be set initially and then changed according to the attributes. For example, the gradient of the terrain (hereinafter referred to as the "terrain gradient") can be calculated based on the elevation of the mesh MS of interest and its surrounding mesh MSs, and the travel speed can be set according to the terrain gradient. Specifically, the greater the terrain gradient, the larger a coefficient (hereinafter referred to as the "speed coefficient") can be set, and the travel speed can be set by multiplying the speed coefficient by the reference travel speed. In this case, it is recommended to divide the terrain gradient into multiple ranges and associate the speed coefficients with them, or to set a relational expression consisting of the terrain gradient and the speed coefficient.

[0031] Alternatively, the movement speed can be set by multiplying the reference movement speed by a speed coefficient corresponding to the type of feature at the location of the mesh MS. For example, if the mesh MS is made of sand, a small speed coefficient is assigned, and if it is made of concrete, a large speed coefficient is assigned. In this case, it is advisable to assign a feature type to each mesh MS and prepare a table showing the correspondence between feature types and speed coefficients.

[0032] (Initial point display means) The initial point display means 101 is a means for displaying one or more initial points on topographical map data displayed on a display or the like. Specifically, when an operator specifies a desired position on the topographical map data using a pointing device or the like, the initial point display means 101 displays the initial point at the specified position. At this time, the operator can specify only one position, or can specify two or more positions. Alternatively, the initial point can be displayed automatically instead of (or in addition to) an operator operation. In this case, the position at which the initial point is to be displayed is set in advance, and the initial point display means 101 displays the initial point at the previously set position.

[0033] (Movement vector setting means) The movement vector setting means 102 is a means for setting a "movement vector." Here, a movement vector is a vector that indicates the estimated position to which a display point (initial point or moving point) will subsequently move, and the length of the vector (hereinafter referred to as "movement distance") is calculated as the product of the movement speed and the movement time, and the movement direction MD of the mesh MS is used as the vector direction. Therefore, the movement vector setting means 102 sets a movement vector for each mesh MS. Note that the movement vector setting means 102 can be configured to set movement vectors for all mesh MS in advance, or can be configured to set a movement vector each time a display point occurs for a mesh MS.

[0034] (Movement point display means) The moving point display means 103 is a means for sequentially displaying moving points on topographic map data displayed on a display or the like. Specifically, a moving point is displayed when a moving time has elapsed since the initial point was displayed, and a new moving point is displayed when a moving time has elapsed since the most recent moving point was displayed. The position at which a moving point is displayed is a planar position that is moved by the movement vector of the mesh that includes the previous display point (initial point or moving point), starting from the previous display point (initial point or moving point).

[0035] In other words, the moving point display means 103 displays additional moving points as the moving time elapses, resulting in a continuous display of many display points. This allows the user to easily and intuitively grasp the flow of surface water. On the other hand, if too many display points are displayed continuously, and if moving points are displayed continuously from many initial points, the flow of surface water may become difficult to understand. Therefore, it is possible to configure the display so that old display points, that is, display points that have been displayed for a long time, are hidden (deleted). Furthermore, particularly in cases where the moving speed is high, the distance between display points (initial points and moving points) becomes large, making it difficult to understand the moving route. In such cases, it is possible to display the display points connected by line segments.

[0036] Furthermore, to make the direction of surface water flow clearer, the display points can be designed to change in shade over time. For example, concentrations 4 to 1 can be set in advance in ascending order of concentration, and as time passes from the time of display, the concentration changes from 4 to 3, and then from 3 to 2. This makes it clear that surface water is flowing from light (pale) display points to dark display points. Of course, instead of gradually changing the shade of the display color, the shade of the display color can be changed continuously, or the color can be changed from light to dark over time.

[0037] (Processing flow) The main processes of the surface water current display system 100 will be described in detail below with reference to Figure 5. Figure 5 is a flow chart showing the flow of the main processes of the surface water current display system 100, in which the central column shows the processes to be executed, the left column shows what is necessary for those processes, and the right column shows what results from those processes.

[0038] When displaying the surface water flow using the surface water flow display system 100, it is advisable to set the display conditions (movement speed, movement velocity, display period, etc.) in advance using the display condition setting means 104 (Step 201 in Fig. 5). Next, the initial point display means 101 displays one or more initial points on the topographic map data displayed on a display or the like (Step 202 in Fig. 5), and the display of the surface water flow begins. Note that the display start can be triggered by the display of the initial point by the initial point display means 101, or by the operation of a separately provided start button.

[0039] Display of the surface water flow begins, and only the initial point is displayed until the travel time has elapsed (No in Step 203 in FIG. 5). On the other hand, once the travel time has elapsed (Yes in Step 203 in FIG. 5), the movement vector setting means 102 sets a movement vector (Step 204 in FIG. 5). Specifically, the movement vector is set based on the movement direction MD of the mesh MS that includes the initial point and the movement distance (movement speed x movement time).

[0040] Once the movement vector is set, the plane coordinates of the position moved by the movement vector from the initial point as the starting point (hereinafter referred to as "moved point coordinates") are calculated (Step 205 in FIG. 5), and the moved point display means 103 displays the moved point at the moved point coordinates (Step 206 in FIG. 5). After the moved point is displayed, only the initial point and the moved point are maintained on display until the movement time has elapsed (No in Step 207 in FIG. 5). On the other hand, once the movement time has elapsed (Yes in Step 207 in FIG. 5), a series of processes (Steps 204 to 207) are executed again. After the display point (initial point or moved point) is displayed, the display is maintained until the display period has elapsed, but once the movement time has elapsed, the displayed point is hidden (i.e., disappeared).

[0041] FIG. 6 is a step diagram that schematically illustrates how the surface water flow display system 100 displays the surface water flow. In FIG. 6(a), the initial point Pst is displayed on mesh MS1 by the initial point display means 101. After the initial point Pst is displayed, when a moving time has elapsed, the moving point coordinates for displaying the first moving point Pm1 are calculated. At this time, since the initial point Pst is displayed on mesh MS1, a moving vector MV is set based on the moving direction MD for mesh MS1, and the moving point coordinates of the moving point Pm1 are calculated based on the moving vector MV and the initial point Pst. Once the moving point coordinates are calculated, the moving point display means 103 displays the moving point Pm1. In this example, the moving point Pm1 is displayed on mesh MS3 as shown in FIG. 6(b). Note that the display color of the initial point Pst has changed from "Density 4" to "Density 3" because time has elapsed since its display.

[0042] After the moving time has elapsed after the moving point Pm1 is displayed, the moving point coordinates for displaying the second moving point Pm2 are calculated. At this time, since the moving point Pm1 is displayed on the mesh MS3, a moving vector MV is set based on the moving direction MD for the mesh MS3, and the moving point Pm2 is displayed at the moving point coordinates obtained by the moving vector MV. In this example, the moving point Pm2 is still displayed on the mesh MS3, as shown in FIG. 6(c). Note that the display color of the initial point Pst has been changed from "Density 3" to "Density 2," and the display color of the moving point Pm1 has been changed from "Density 4" to "Density 3."

[0043] After the moving time has elapsed after the moving point Pm2 is displayed, the moving point coordinates for displaying the third moving point Pm3 are calculated. At this time, since the moving point Pm2 is still displayed in mesh MS3, a moving vector MV is set based on the moving direction MD for mesh MS3, and the moving point Pm3 is displayed at the moving point coordinates obtained by the moving vector MV. In this example, the moving point Pm3 is displayed in mesh MS4, as shown in FIG. 6(d). Note that the display color of the initial point Pst has changed from "Density 2" to "Density 1," the display color of the moving point Pm1 has changed from "Density 3" to "Density 2," and the display color of the moving point Pm2 has changed from "Density 4" to "Density 3."

[0044] After the moving time has elapsed after the moving point Pm3 is displayed, the moving point coordinates for displaying the fourth moving point Pm4 are calculated. At this time, since the moving point Pm3 is displayed on the mesh MS4, a moving vector MV is set based on the moving direction MD for the mesh MS4, and the moving point Pm4 is displayed at the moving point coordinates obtained by the moving vector MV. In this example, the moving point Pm4 is displayed on the mesh MS2 as shown in FIG. 6(e). Note that the display color of the moving point Pm1 has changed from "Density 2" to "Density 1," the display color of the moving point Pm2 has changed from "Density 3" to "Density 2," and the display color of the moving point Pm3 has changed from "Density 4" to "Density 3." The initial point Pst is hidden because the display period has elapsed.

[0045] After the moving time has elapsed after the moving point Pm4 is displayed, the moving point coordinates for displaying the fifth moving point Pm5 are calculated. At this time, since the moving point Pm4 is displayed in the mesh MS2, a moving vector MV is set based on the moving direction MD for the mesh MS2, and the moving point Pm5 is displayed at the moving point coordinates obtained by the moving vector MV. In this example, the moving point Pm4 is also displayed in the mesh MS2, as shown in FIG. 6(f). Note that the display color of the moving point Pm2 has changed from "Density 2" to "Density 1," the display color of the moving point Pm3 has changed from "Density 3" to "Density 2," and the display color of the moving point Pm4 has changed from "Density 4" to "Density 3." The moving point Pm1 is hidden because the display period has elapsed. [Industrial Applicability]

[0046] The surface water flow display system of the present invention can be particularly effectively implemented when taking measures for utilizing surface water, water balance, etc. Considering that the present invention contributes to the sharing of information and ultimately contributes to the maintenance or restoration of a healthy water cycle, the present invention can be said to be an invention that can be expected to not only be used industrially but also to make a significant contribution to society. [Explanation of symbols]

[0047] 100 Surface water flow display system of the present invention 101 (Surface Water Flow Display System) Initial Point Display Means 102 (Surface Water Flow Display System) Movement Vector Setting Means 103 Moving point indicator (of surface water flow indicator system) 104 (Surface water flow display system) display condition setting means 105 Topographic map data storage means (for surface water flow display systems) 106 (Surface Flow Display System) 3D Terrain Model Storage Means 107 Display condition storage means (for surface water flow display system) MD movement direction MS Mesh MV Moving Vector

Claims

1. A system for displaying surface water flow using topographical map data set in a plane coordinate system and a plurality of meshes set within the entire or partial range of the topographical map data, Each of the meshes has three-dimensional coordinates, and a movement direction is set based on the surrounding meshes; an initial point display means for displaying an initial point at one or more positions in the topographical map data that are predetermined or designated by an operator; a movement vector setting means for setting a movement vector based on the movement direction, a predetermined movement speed and a predetermined movement time; a moving point display means for displaying a moving point at a position to which the initial point has moved by the movement vector related to the mesh including the initial point when the movement time has elapsed after displaying the initial point, the moving point display means displays a new moving point at a position where the moving point moves by the movement vector related to the mesh including the latest moving point, each time the moving time elapses. A surface water flow display system.

2. the initial point display means terminates the display of the initial point when a preset display period has elapsed after the display of the initial point; the moving point display means ends the display of the moving point when the display period has elapsed after displaying the moving point.

2. The surface water current display system of claim 1.

3. the initial point display means changes the shade of the display color of the initial point as time passes after the initial point is displayed; the moving point display means changes the density of the display color of the moving point as time passes after the moving point is displayed.

3. The surface water current display system of claim 2.

4. a display condition setting means for setting the moving speed and / or the moving time by an operator operation; The moving speed and / or the moving time can be changed using the display condition setting means even while the moving point is being displayed by the moving point display means.

2. The surface water current display system of claim 1.

5. For each of the meshes, a terrain gradient is calculated based on the three-dimensional coordinates of the mesh and the surrounding meshes, and a speed coefficient is set according to the terrain gradient; The moving speed for the mesh is set as a value obtained by multiplying the preset moving speed by the speed coefficient for the mesh.

2. The surface water current display system of claim 1.

6. A speed coefficient is set for each mesh according to the type of feature related to the mesh, The moving speed for the mesh is set as a value obtained by multiplying the preset moving speed by the speed coefficient for the mesh.

2. The surface water current display system of claim 1.

Images