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I have two rasters. One is larger and binary called mask (all values are either 0 or 1). The smaller raster fits inside this raster but has a much smaller extent smallerMask. All its values are 1. Where it sits above the larger raster, the larger raster is populated with 0s. I want to replace that area of 0s with the 1s from the smallerMask. Thought this would be easy.

(("mask" + "smallerMask") = 2 OR ("mask" + "smallerMask") = 1) = 1

However, I just get output along the smaller raster extent. I made sure that the larger one was selected as the extent. Why is this happening?

I've also tried merge but it keeps the original values.

EDIT: I figured out a workaround by using both layers to build a virtual raster but I would really like to know how to do this with raster calculator

1 Answer 1

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Okay, I figured this out.

  1. Ensure the smaller raster actually has the same extent as the larger raster, but with a bunch of nodata values outside the AOI.

  2. use r.null to convert the nodata to 0s in the smaller raster.

  3. Use the following expression in raster calculator:

(("mask1" + "mask2") = 2 OR ("mask1" + "mask2") = 1) = 1

And that's it.

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