The Research And Realization Of Electronic Sand Table Based On Quadtree Algorithm

In accordance with the actual needs of the operating sand table,we have designed the electronic sand table and realized its main functions in paper,which uses quadtree algorithm and OpenGL function in Visual C + + programming environment.Paper loads DEM terrain data on the accuracy of the map 0.01-0.04 cm making use of quadtree algorithm in the technology of detail level.Based on distance evaluation system,we generated different resolution of the topography in accordance with the different point of view. According to the experimental,the control parameters C is 64,which is the largest frame rate in the 6 groups of experimental data.Paper draws the sky with the cylinder method and realizes the three-dimensional topography in two modes which are texture mapping and grid, marks the objects in the way of loading the two-dimensional objects.On the issue of displaying point coordinates,paper proposes a fast way to get the Z value against the literature[1]having proposed the complexity algorithm of three-dimensional coordinates mouse to get the coordinates(RIP algorithm) in theory.The way uses glReadPixels 0 function to read the value of Z buffer instead the way of mathematical methods by RIP algorithm,and uses gluUnProject 0 function to convert the coordinates of OpenGL two-dimensional to three-dimensional coordinates.Combined with DEM data,paper amendes the spatial coordinates to get the geographical coordinates.The improved algorithm simplify the procedure,enable to read the actual point coordinate and enhance the practicality of electronic sand table.By changing the viewpoint to achieve roaming function.Through the overall scaling of electronic sand table sand table or setting the scale of it,we can see the electronic sand table conveniently.Paper uses access database and ADO connection method to achieve geographic information.Paper uses the two spherical distance formula to measure the distance between two points in the Earth's surface and uses the visual analysis between two theories to judge whether two visual.The result shows that the electronic sand table can achieve the marking,querying, roaming and terrain analysis functions.1:1000 scale in the level of conditions,the map accuracy is 0.134 centimeters and the frame rate is 28.369 frames / seconds,which meets the actual needs of the operating sand table.The electronic sand table sand table can be used for training and exercises and so on.