I'm setting up a graphic modeler to handle three vector layers and one raster layer. In the end, I hope to vectorize the raster and merge the other three into one coverage. The raster file is a slope DEM, and I'm looking for anything steeper than a 25% grade.
I'm pulling my hair out because every time I use the 'select by expression' tool, the next step is to save the selection. Of course it tells me that nothing has been selected. I've tested my expression...
"Shape_Area">2000 AND "DN" = 1 (DN is the binary value attributed to slope < or > 25 degrees)
...outside of the graphic modeler and it works just fine. In debugging, I went back and saved the vectorized file with the
$area field calculation included, and the 'select by expression' works just fine.