Calculating Building Height in LP360

[gisgal]

I have a LAS file classified with Ground and Unclassified points only.  In addition I have a point and a polygon layer of building locations.  Is there a way to calculate building height without using the extractor extension?  I can classify the building points using the building polys but what I can't figure out is how to subtract the z: value of the surrounding ground from the z: value of the building LAS points to get a height calculation.  Is that something that is possible in LP360 or some combination of LP360 and 3-D analyst?  If so does anyone have documentation on how to complete that task?  Thank you.

[toonp]

I don't think there is a simple solution for that, but with the aid of 3D analyst and some scripting in python, a workaround can be done. What i did is:

1) export the LIDAR ground points in LP360 as a raster (IDW interpolation for smoother surfaces) and with a relative smal resolution (e.g. 10 meter)
2) import the raster in arcgis and do a "raster to point" conversion
3) execute a "spatial join" with the building polygons where you put the match option on "intersects" and with a search radius of e.g. 10 meters. Then you have a good mean value of the ground area surrounding the building.

For finding the building height a same kind of workaround can be done by exporting the LAS points that fall within the builidng polygon (e.g. extractor module can additionally classify points that are within roof planes)
With the "lastomultipoint" tool in arcgis, you create a shp file of these points and a spatial join with match option set on "Contains" and setting the fieldmapping to maximum, minimum, mean, standard deviation,... gives you the statistics of the points that fall within the building polygon. The heights of the building can then easily calculated.