I have a VRT mosaic file I made from thousands of ESRI GRID files.

It looks something like this.

<VRTDataset rasterXSize="111831" rasterYSize="94785">
  <SRS dataAxisToSRSAxisMapping="1,2">PROJCS["unnamed",GEOGCS["Unknown datum based upon the GRS 1980 ellipsoid",DATUM["Not_specified_based_on_GRS_1980_ellipsoid",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6019"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4019"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",24.3333333333333],PARAMETER["central_meridian",-81],PARAMETER["scale_factor",0.999941176470588],PARAMETER["false_easting",656166.666666667],PARAMETER["false_northing",0],UNIT["Foot_US",0.304800609601219],AXIS["Easting",EAST],AXIS["Northing",NORTH]]</SRS>
  <GeoTransform>  6.9303750000000000e+05,  2.5000000000000000e+00,  0.0000000000000000e+00,  9.5992000000000000e+05,  0.0000000000000000e+00, -2.5000000000000000e+00</GeoTransform>
  <VRTRasterBand dataType="Float32" band="1">
      <SourceFilename relativeToVRT="1">be_rasters/692500_725000</SourceFilename>
      <SourceProperties RasterXSize="785" RasterYSize="1000" DataType="Float32" BlockXSize="256" BlockYSize="16" />
      <SrcRect xOff="0" yOff="0" xSize="785" ySize="1000" />
      <DstRect xOff="0" yOff="92968" xSize="785" ySize="1000" />

Of course, my real file has thousands of ComplexSource elements. When opened in QGIS, it shows the elevations of every property in a U.S. county.

Here's how part of it looks in QGIS.

enter image description here

How do I obtain the elevation levels of each property, in feet or meters, from the VRT mosaic?

  • 1
    How do you first identify the location of each property? Do you have a vector file of property locations? Or is this something you want to infer from the DEM?
    – Spacedman
    Sep 1 '19 at 21:09

Assuming you have a vector polygon dataset of property boundaries, you can extract a statistical summary of the elevation values in each polygon using the Zonal statistics processing tool:

Calculates statistics of a raster layer for each feature of an overlapping polygon vector layer.


The available operators are:

  • Count
  • Sum
  • Mean
  • Median
  • St. dev.
  • Min
  • Max
  • Range
  • Minority
  • Majority (mode)
  • Variety
  • Variance
  • All

You could also use the Zonal histogram processing tool, but its output is not very useful because of a poor design choice (in my opinion) to output a new column for every single unique value in the raster that intersects with the polygon dataset.

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