[GIS] QGIS Raster Calculator, joining two raster

qgisrasterraster-calculator

In QGIS raster calculator I do:

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Plus (+)

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And I get:

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The red circle in the middle is like cut in the result, QGIS it's not adding every pixel on each raster, it makes a kind of intersecction…

If i select in the QGIS layer selector the two layers to be added (using blending effects = multiply) i get visually pretty much what I spected to see when making the raster calculation adding:

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How could I make a real adding calculation between two rasters?

Best Answer

Try to replace your Nodata values with 0 and repeat your calculation. To do that you could try: Change NODATA pixel value in raster to arbitrary value.

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[GIS] Raster Calculator in QGIS returning ‘nan’ values

The Copy Raster tool in ArcGIS was used to convert the Pixel Type of one raster (8 bit unsigned) so that it matched the Pixel Type of the other raster (32 bit unsigned).

The Raster Calculator then worked perfectly to add the two rasters together.

[GIS] Compare two raster extents in QGIS

You can use the QGIS raster calculator for this, using boolean masks. An example:

(("grid1@1">0) AND ("grid2@1">0)) * 1
+ (("grid1@1"=0) AND ("grid2@1">0)) * 2
+ (("grid1@1">0) AND ("grid2@1"=0)) * 3
+ (("grid1@1"=0) AND ("grid2@1"=0)) * 4

where you can change 1, 2, 3, and 4 to be whatever values you like.

The way that this works is that the first part of each term is a boolean mask. ("grid1@1">0) AND ("grid2@1">0)) is True when your first condition is met, and it can be multiplied by your categorical value D (I used 1). The next three terms match your next three conditions.

Note

Steven Kay notes in the comments that the same expression can be performed without using AND by replacing it with a *. In this case, the first term looks like

(("grid1@1">0) * ("grid2@1">0)) * 1

Best Answer

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Note

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