demprep

This program performs the necessary preparation of a DEM file so that it can be used as a shape model. The method used to find the intersection of a look vector with a DEM surface has recently changed (9/2010) to take care of problems that were encountered at the poles of the DEM file that were caused by artifacts generated near the poles when the DEM was produced. This new intersection algorithm requires that the DEM have a padded line at any pole that exists in the DEM file. If the DEM is a global DEM, then the left and right edges are also padded with a single column of pixels. The padding allows the bilinear interpolation to work properly at the poles. The new algorithm also requires that the DEM have a table blob in its labels ("ShapeModelStatistics") which contains the minimum and maximum radii that occcur in the DEM file. This information is required in order to bracket the solution where the look vector intersects the DEM. This information helps to make the algorithm run much faster. The DEM is required to be a Planetocentric file in Simple Cylindrical projection. If it is not, then the demprep program will fail. This program will first check to see if the DEM has been padded. If padding has already occurred, then no further padding will be added. It is not valid to run this program on anything but a DEM. This program can be run on files with non-Equatorial projections. If the file is non-Equatorial, then it cannot be padded. However, the program will add the ShapeModelStatistics table blob to the DEM file labels.