ISIS Application Documentation
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This program prepares DEMs for use as shape models. It is not valid to run this program on anything but a DEM.
Description
Categories
Groups
History
Description
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.
Categories
Parameter Groups
Files
| Name | Description |
|---|---|
| FROM | Input DEM cube |
| TO | Output padded DEM cube |
Files: FROM
Description
The DEM cube which will be padded
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
Files: TO
Description
| Type | cube |
|---|---|
| File Mode | output |
| Filter | *.cub |
History
| Steven Lambright | 2008-09-15 | Original version (demwrap) |
| Steven Lambright | 2008-10-03 | Added additional checks for valid projections and fixed the implementation of the north and south poles. |
| Janet Barrett | 2010-09-09 | Original version (demprep) Used the demwrap program as a model for the demprep program. |
| Janet Barrett | 2011-02-18 | The padding at the poles is no longer set to the average value of the line below or above the padded line. In order for the ray tracing routine in the Sensor class to converge when it is right at the poles, the padding had to be changed in the following way: At the north pole, the average of the pixels that lie in the first line of the file is calculated. Then, each pixel in the top padded line is set to 2*average - the pixel below it. At the south pole, the average of the pixels that lie in the last line of the file is calculated. Then, each pixel in the bottom padded line is set to 2*average - the pixel above it. This change only applies to those DEM files that cover the poles. |
| Steven Lambright | 2011-03-18 | Fixed handling of special pixels. Now reports the min/max radius encountered. A negative radius will now cause this program to fail. |
| Janet Barrett | 2011-07-05 | Modified the program so that it works with files that have non-Equatorial projections. These types of files will not be padded. They will only have the ShapeModelStatistics table blob added to their labels. Several programs are looking for the ShapeModelStatistics table blob to determine if the file is a DEM. |
| Debbie A. Cook | 2012-12-10 | Changed to use TProjection instead of Projection. References #775 |
| Kristin Berry | 2014-05-30 | Fixed padding for special pixels. References #1010 |