Geographic Information Systems Asked on April 12, 2021
Say, I have a raster with some annual statistics data.
Then
Daily avg = Annual / 365
Weekly avg = Annual / 52
Monthly avg = Annual / 12
I know I can do this via Raster calculator in QGIS (v2.18.15). However, there is always a new output. Therefore I am looking for more convenient to do it on-the-fly. Is there some tool to manipulate raster data settings?
For vector data, there is Query builder (in Layer Properties -> General) to exclude or manipulate the dataset (which is not exactly the same, but does a great job with data).
After some time I found a partial solution to this via building a VRT file (see more specification) and setting the
<scale>
<offset>
+ some more can be added in
<ComplexSource>
Example of DEM scaled from [m] to [ft]
<VRTDataset rasterXSize="800" rasterYSize="800">
<SRS>GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY["EPSG","4326"]]</SRS>
<GeoTransform> -6.2000000000000000e+01, 2.5000000000000001e-03, 0.0000000000000000e+00, 1.5000000000000000e+01, 0.0000000000000000e+00, -2.5000000000000001e-03</GeoTransform>
<Metadata>
<MDI key="AREA_OR_POINT">Area</MDI>
</Metadata>
<VRTRasterBand dataType="Int16" band="1">
<NoDataValue>nan</NoDataValue>
<ColorInterp>Gray</ColorInterp>
<scale>3.28084</scale>
<SimpleSource>
<SourceFilename relativeToVRT="1">DEM_meters.tif</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize="800" RasterYSize="800" DataType="Int16" BlockXSize="800" BlockYSize="1" />
<SrcRect xOff="0" yOff="0" xSize="800" ySize="800" />
<DstRect xOff="0" yOff="0" xSize="800" ySize="800" />
</SimpleSource>
</VRTRasterBand>
</VRTDataset>
Unfortunatelly, it seems that GDAL has not good support to write into VRT (I add this line to XML manually). There is some promising feature from just released GDAL2.3 in
gdal_translate -a_scale ...
(still to be tested, yet)
Answered by jurajb on April 12, 2021
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