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I am trying to clip a raster DEM between two elevations, specifically a portion of the contiguous United States in an SRTM 90m DEM.
I would like to create a vector polygon mask that overlies the all parts of the DEM that lie between two elevations; for example, between 1000m and 2000m.
At the moment I have downloaded the SRTM section I need in both ASCII and GeoTIFF formats. I am using QGIS 2.18.15.