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I have a single band raster layer, namely the USGS Global Mountain Explorer Home K3 dataset.
It is a 8 bit unsigned integer GeoTIFF of 200 Mb, with 4 grey values each corresponding to a mountain height.
What is the correct way to split this layer into 4 different layers so that I can vectorize them separately?
If I mess around with transparency and then I try to save the rendered images the results are huge, even with high compression.
You can use raster calculator to split the image in 4 different rasters each with 0 and 1 values and then vesctorize each one of them.
Check the values of your original raster and use them in an expression, something like"image@1" = 0.5. After you vectorize the image you'll just have to remove the polygon that corresponds to 0 value.
But I would suggest using 'Vectorising grid classes' function and specify the class by the grey value. You would still need to execute this 4 times, but it's faster, since you don't need to clean up.
