I am using the BirdLife International .gdb file (polygons) of bird species distributions to try and make a species richness map across the Brazilian Amazon. To do this I have clipped the global distributions file to my study area. I have also created a hexagonal grid of my study area.
My method so far has been to intersect these two layers to split the distributions into the hexagonal grid cells. From this I am getting the polygon centroids and counting the number of points in each of the original hexagon cells. This has already worked for the IUCN mammal and amphibian shapefiles.
However, when I try to intersect the birdlife distribution layer with the hexagonal cells I get an invalid geometry error even though I have validated the geometries using the QGis Validate geometries tool, and removed invalid geometries.
error invalid geometry detected in input layer A, feature 42
I have also tried checking the geometries in ArcMap10 and they appear to be valid. The problem also continued after deleting the features the error message highlighted.
Is there a method that would avoid this error or would solve this problem?