A Pox on Both Your Houses--Where to Get COPDEM
(post updated, most recently 30 January) The Copernicus DEM (CopDEM) is the best of the free global one arc second DEMs (Guth & Geoffroy, 2001; Bielski and others, 2003). FABDEM and Diluvium DEM are beyond the scope of this discussion, but I think there are caveats about what they do well and how they degrade CopDEM for some applications.. So where you do get CopDEM, and if the supplier changes the DEM is it still CopDEM or should users be warned about the changes? The are in fact changes in some sources for CopDEM, some of which are probably benign, and some of which are potentially serious. Excuse me if this gets technical, but you need to understand what is being transformed before you get CopDEM. If you want just the conclusion, use the cookie cutter CopDEM exports from OpenTopography with caution, and it should have a clear indication that it changes elevations. IMPETUS for this WORK A colleague, Sebastiano Treviasani, reported a shift in CopDEM downloaded from Open...