Creating planes, eg roof surfaces, from LiDAR/DSM data

Question

I am capturing the area of roof tops of buildings from a DSM (derived from LiDAR data) which has not been much of a problem. I can then also derive angle, hillshade and aspect but it is only per-pixel.

What I need to do is create the actual roof planes (either as raster or polygons) and I just don't know how to do it.

I've read a lot about cluster analysis, using nearest neighbour etc. I've also read creating a TIN from the raw points, would this work? and if so, would this need to be created instead/before a raster of the DSM?

Creating planar surfaces of roofs, just not sure.

Answer 1

I think you can use some segmentation techniques to create objects and than select roofs and non-roofs. You can find a good material about segmentation techniques and some open source softwares here.

PS 1: You have also some packages in R to perform image segmentation: there are EBImage and biOps. The EBImage manual is a good way to start.

Answer 2

id take this approach.

get roof polygons.

extract your lidar points from the polygons.

i would filter the points for one return only

then build the tins (youll need a handful of points per roof minimum).

lastools can do it as a one step process