In order to calculate the terrain points (Xi, Yj) on the elevation value, generally first discovered from the DEM terrain data grid to which it belongs, and then the elevation value using a grid intersection, and quadratic linear interpolation function to calculate the elevation value. But this approach must always be from the vast amount of DEM terrain data searches for a specific grid, and at present the search algorithm for optimal time not less than the log (n). Calculation in order to take full advantage of the computer's shift characteristics of Article 2I times zoom in or zoom out of DEM terrain data grid solution. This method omits the grid search procedure, which greatly improves its performance. Its principle is shown in Figure 4: Zoom image, reduce the number of raster 1 time, need to merge the four adjacent grids. Which virtual slash represents the grid and contours, black thick line indicated by the contours of the new grid is calculated.