I have a point cloud captured with an SX10 down a local road (about 5 scans in total) and I am attempting to calculate some power line clearance heights.

I have used the "Extract Line Feature" command to create a CAD line however when I run the "Measure Line Clearance" command I keep getting the following error:

Video showing creation of power line and failed attempt and measure line clearance:
Power Line Clearance
If any one has seen this error before or can point out what i am doing worng, it would be greatly appreciated.
Thanks,
Ed