I am working in QGIS 3.0.2-Girona.
I am digitizing images in which there are rocks that can be encrusted, totally or partially, by algae. I want to have a polygon for the rock and one for the algae. In particular I can have 3 cases:
- the polygon of a rock and the one of the algae coincide
- the polygon of a rock could potentially contain more than one polygon of the algae
- the polygon of a rock could contain NO algae polygon(s) at all.
For this reason I thought that one effective way to go is to have 2 polygon vectors open in edit mode: 1 for rock and 1 for algae. When digitizing a rock with algae, I digitize the rock first and then copy paste the Geometry only (i.e. without attribute) to the algae vector layer. Repeat this process whenever I find a similar case while digitizing.
My problem is that selecting a feature and copy/paste it to a different layer doesn't seem to work: although the 2 layers are in edit mode, when I paste the geometry to the target layer I can see the pasted feature in its attribute table (with just the ID value, that's OK) but it doesn't appear on the map. If I select the feature in the target layer's attribute table, and click "zoom to selection", I am shown a white part of the map (I don't even know where) clearly not in the same position as the copied polygon.
Am I doing something wrong? Does anybody have a strategy to achieve this task?