My question is about the calculator in the QGIS graphical modeler. I explain my problem issue first:
I want to build a modeler that creates buffers around layers and makes a selection on a second layer if the polygons are inside the buffers. You see a picture of that modeler here under.
In fact, my modeler is working well until I add a calculator. My input layers are in WGS84 projection, that's why the buffer is measured in decimal degrees. I want to add a calculator that divides the distance by 111 (approximately) so that I can seize the distance in kilometers in the input field.
The calculator is a modeler function that specially exists for that issue of modifying numerical values (entered by the user or generated by some other algorithm). The documentation only said to use the modelers value as a variable. So, I tried differents syntaxes:
a / 111 Distance1 / 111 Distance1 / 111 "Distance1" / 111
etc. But I always get the same error message:
According to some discussions, it means that the assignment of the variable is not understood what seems logical to me. Can anybody share experiences of the use of the Calculator in the graphical modeler with me?
The documentation about longer function series in the modeler is not so good, that's why I didn't find any tutorial that uses the calculator.
How should I define my variables well? I am using QGIS Essen as I changed my computer recently, can this be a source of problems and I should go back to QGIS Vienna stable version?