Landscape vector overlay if vector polygons have "holes"

[Martin-Jung]

The Landscape vector overlay function does not work if polygons have internal "holes" within them

This is a "known" bug as LecoS is unable to compute metrics to Multi-polygon features. By adding a hole to a polygon you are changing its type from WKB_POLYGON to WKB_MULTIPOLYGON (because It now has additional boundary nodes).

There is no easy fix for holes yet and this requires a lot more work which is why LecoS is currently unable to compute metrics for Multipolygons. What it technically need to compute is to clip out all raster parts between the individual features and mosaic them together. If the features of a Multipolygon are spatially seperated than you could split them into individual parts before the computation.

Todo:

• Write a new subroutine that loops through individual WKB_polygons of a WKB_multipolygon and find a way to combine their results