Inferior Terrain Flattening results when using external DEM

[johntruckenbrodt]

Terrain-Flattening results in garbage when using Copernicus 30m (Auto Download)

The reason that the TF result obtained using auto downloaded Copernicus 30m DEM is different from that obtained using external Copernicus 30m DEM file is that the DEM oversampling factor is computed differently. The oversampling factor is computed using the DEM resolution and the image pixel spacing. In the former case, the DEM resolution is given while in the latter case the DEM resolution is computed using Earth model. We have updated the oversampling factor calculation so that it is the same …