| 摘要 |
<p>A method for presenting intervisibility data relative to an observation point (O). A data base of terrain altitudes (Z) is stored in a computer memory. The data base comprises terrain altitudes (Z) at a grid of points in a selected terrestrial area encompassing the observation point (O). Visible height from the observation point (O) at the grid points (J, I) are derived from the data base with a computer by performing a number of steps grid point (J, I) by grid point (J, I+1) in succession in an order moving away from the observation point (O). The first step is to determine a projected height at the grid point (J, I) from the visible heights between the observation point (O) and the grid point (J, I). The second step is to compare the projected height (ZP) with the terrain altitude (Z) at the grid point (J, I). The third step is to select as the visible height at the grid point (J, I) the larger of the compared terrain altitude (Z) and the projected height (ZP). A number representative of the visible height at each grid point (J, I) as so derived with a computer is stored in the computer memory. The computer memory is coupled to a visual display device to present the stored representations of the visible height in spatial relationship coordinated with the spatial relationship of the grid points (J, I) of the terrestrial area. The visible height data is derived by use of the similar triangles theorem, and interpolation of previously calculated visible heights.</p> |
