Problem with LAS files - time layers at different heights?

[Ewanc]

Its easier to explain in a picture

Image1.jpg (271.82 KiB) Viewed 3452 times

Here are 3 of the 48 tiles I have. The front one has 3 layers split off, and the other 2 tiles have 2. They should all be at the same height to make a solid terrain.

The back story is; I got most of Pikes Peak from http://coloradogeologicalsurvey.org, and some of the files are in LAS Version 1.2 and perfect, but a majority are in 1.4 and have some problems. I was able to open the 1.4 files with CC 2.10 alpha, but they are still a mess as you can see, and I'm not sure what the problem is, or how it can be fixed, other than to segment off the top and bottom layers and hope there is still a complete set of ground points.

[daniel]

Did you always use the same 'Global shift' for all files? You must set it to 'last input' (for the second and third cloud) otherwise CC will use the default LAS shift (which is specified in LAS files) and it may be the same for all 3 clouds.

[Ewanc]

Good guess, but it's happening even with one tile loaded. I hit the apply all and yes to all buttons while loading and the others are lining up perfect with the first; but they also have the same misaligned layers.

Ive been able to work around it by loading a few tiles, merging them, then switching to side view and segmenting off the garbage. Only one of the layers of the LIDAR cake forms a complete terrain, so it was an easy decision which to keep. To my relief, I was able to use the classification scalar field to isolate all of the ground points from it.

pikes_new_lidarafter.jpg (298.98 KiB) Viewed 3436 times

[daniel]

Oh that's strange. Does it mean the problem comes from the files?

[Ewanc]

I just tried opening them in a couple viewers and the extra layers show up there too. Its added a couple extra steps to my workflow, but at least its workable.