PDAL pipelines and getting the difference

Question

I have 2 overlapping point clouds - A.las and B.las.
A is from 2015 and B is from 2016, both are from the same area. I have PDAL (through OSGeos4W64), I'm trying to create a new file containing all the points which are different, this can be in two files i.e. A_diff and B_diff or as a single All_diff.

I've tried to use diff within pdal and pcl, but I'm not sure how to write the syntax of the json file, the www.pdal.io site is not great for beginners. Can anyone provide me with an example?

Heres the pcl info http://docs.pointclouds.org/trunk/classpcl_1_1_segment_differences.html

Thank you for any help.

Answer 1

It is not possible to do this as a PDAL pipeline with the current suite of stages.

The problem is that all reader stages will be subject to the same filter stages (not entirely true, there is a concept of branching pipelines, but it is not widely used). Regardless, there is no way to query one input cloud from another in the pipeline setup. The only workaround that comes immediately to mind would be to develop a custom filter that accepts as one of its inputs the filename of the cloud to query against. We do something similar when colorizing points from a raster. You'd have to develop two pipelines (A to B, and B to A) and write the partial diffs.

I think the easiest way forward is to create a new PDAL kernel that does exactly what you need.