I use the Point Sampling Tool in QGIS to transfer gridvalues (of DEMs) to point features. This goes well with grids from f.i. MapMart (SRTMHARRIS_DEM), but I get only NULL-values when using grids from USGS (SRTM 1 Arc-Second Global). Does anybody know why and how to get proper values from SRTM 1 Arc-Second Global?
Yes, AndreJ, you are right, thanks. For applying the “Point sample tool” the maps and grids should align with OTF off. After transforming the maps/grids to the same (Project) CRS (with "save as") everything went fine.