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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?

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    Are you sure that DEM and point layer are in the same CRS? I.e. turn OTF OFF and see if they still align. – AndreJ Jul 3 '15 at 18:00
  • I tried different CRSes which might apply, but using others the maps do not align. So I would think the CRSes are okay. – Jan Hoogendoorn Jul 3 '15 at 18:17
  • Mmm, yes, with OTF off the maps don't align. I need some more study. How to transform a map/grid from one to the another CRS? – Jan Hoogendoorn Jul 3 '15 at 18:38
  • In QGIS, Raster -> Projection -> Reproject to another file name and the CRS of the point file. For vector layers, you can use Save As ... to the CRS of the raster. – AndreJ Jul 3 '15 at 19:00
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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.

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