Multiple levels of detail environment modeling for radio propagation simulation and prediction

Digital elevation models (DEM) or digital terrain elevation models (DTED) are widely used in radio propagation simulation and prediction. The resolution of DEM´s is getting higher and higher with the latest resolution of centimeters generated by LIDAR (light detection and ranging). These high resolution DEM´s provide more realistic representation of the environments and will enhance the accuracy of propagation modeling results. But they also have some drawbacks. First, the storage of high resolution DEM´s will cost large computer disk space and slowdown the I/O process. Second, not all propagation scenarios need high resolution DEM´s depending on the frequency and range. Third, the DEM´s do not explicitly have the three dimensional (3D) information about topographic structures, such as ridges, which is physically important in diffracted field calculations. For example, 3D ridges are key contributors of diffracted field in certain mountainous regions. But many widely used and DEM-based methods (e.g., knife-edge models) ignore the 3D features. Our previous work has shown that the orientation and interior angle of a ridge can cause 3dB difference in path loss prediction for a single ridge. For two ridges, the difference is almost doubled.