Hi @AbdelghaniTamort . I am the developer of the reconstruction algorithm (implemented in geoflow) that underpins 3D BAG and that we have used for both the current version and version 21.09.8 of 3D BAG.
There could be a number of reasons for a building that exists in AHN3 not to be present in 3D BAG. For example:
- building does not exist in the BAG dataset (our source for the building footprints). We only reconstruct buildings that exist in the BAG.
- The pointcloud is not adequate. Eg, there are not enough suitable points to reliable extract a roofplane. This can happen for example for very small buildings and/or insufficient point coverage for that building due to eg. occlusion effects in the pointcloud or other issues.
To know what exactly is the reason these buildings are missing here, I would have to look into it in more detail. But this should give you some general idea about why buildings can be missing.