Redefine Nodata Value to Zero in QGIS – Handling Imagery Nodata

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I have an image which I clipped with an AOI polygon. The contour area was set to pixel value = 0 and I have a nodata value of -32768. I want to redefine the nodata value into zero. I used to do this with ArcMap easily in the raster calculator, but in QGIS I don't see how I could do it. Any ideas?

Best Answer

In QGIS, you can use Raster Calculator with the following calculation:

("your_raster" != -32768) * "your_raster"

With this calculation, if the cell value is -32768 you will get a 0 in that cell and if it is different from -32768 the cell will keep the value it had.

Related Solutions

QGIS Raster Nodata Value – Setting Pixels with Value <= 0 to 'Nodata'

It can be done in one step in QGIS in the raster calculator.

In QGIS3, for a raster layer named "x", use the following expression:

(("x">0)*"x") / (("x">0)*1 + ("x"<=0)*0)

This trick maps raster values x>0 into the ratio x/1 = x, and raster values x<=0 into the ratio 0/0 = NaN. This NaN is rendered as FLOAT_MIN (aka -3.402832...e+38) if the raster is 4-byte float.

Strangely this question seems to have been around a while, with (as far as my quick Google search today shows) most respondents saying it can't be done in a single step. It certainly shouldn't need to be hacked like this. The QGIS documentation could be better too.

[GIS] 16-Bit to 8-Bit and NoData value

You can use the Set Null tool in ArcGIS (Spatial Analyst, so use your 9.x version) - see http://resources.arcgis.com/EN/HELP/MAIN/10.1/index.html#//009z00000007000000. If you generate a classified raster where 1 is your study area and 0 isn't, then you can set the corresponding 0 area in your other raster to Null.

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Related Solutions

QGIS Raster Nodata Value – Setting Pixels with Value <= 0 to 'Nodata'

[GIS] 16-Bit to 8-Bit and NoData value

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