Define additional ground planes in a multilayer process

Use the layer-level parameter

The LDF manual documents IsGP = True for an auxiliary ground-plane layer. Define it in the relevant layer block when the physical process has multiple ground-plane layers.

IsGP also controls cropping behaviour with CropGP. Labelling a layer as a ground plane is not proof of an electrical connection between separate planes.

Check boundaries and connectivity

Inspect the generated planes, openings, vias and return-current paths. Review the main GPLayer and the crop/overhang settings where applicable. Keep enough surrounding geometry to avoid a boundary-dominated result and confirm with a controlled comparison.