Methods to process and mosaic overlapping DEMs

In the case where it is desirable to mosaic overlapping DEMs, it may be necessary to process the data prior to mosaicking, in order to reduce the effects of 'seams' along the overlapping border. A couple of suggestions would be the following:

1. If performing DEM Extraction through ENVI, try to select a significant amount of GCPs in the overlapping areas of the stereo images. This will improve the accuracy of the extracted elevation values along the border, so that a seam is less likely or less noticable.

2. If you are performing DEM Extraction through ENVI without GCPs, you may generate some pseudo GCPs in the overlap area using the first DEM result, and then use the pseudo GCPs during the second stereo pair DEM extraction. This will also improve the accuracy of the relative elevation values between the two DEMs and reduce the effects of a seam.

3. If you are using post-extracted DEMs or DEMs from other sources, select DEM post values with the same x/y coordinates and calculate a scale and offset for these values through linear regression. Then apply the scale/offset values to the second DEM data and perform color balancing in the mosaic process.

Review on 12/31/2013 MM