LiDAR Editing Freak!

So, I have been working with the guys to keep my feet wet with LiDAR data editing so that I understand more about what it takes to prepare the LiDAR surface for delivery to the client or for an ortho surface.  I got my share of data and headed off to edit my surface…

Sounds pretty easy, right?  Well, it actually is as long as you know what to look for.  Our data for this project had a lot of low points in it – due mostly to the fact that we are shooting down stormwater grates in neighborhoods.  This creates low points in the data that is not indicative of the true terrain.  We usually filter these out using our filtering algorithms, but sometimes these points still exist in the data and need to be edited out.

The first way to identify a low point is to create a TIN of the surface.  If there are low points, the TIN will be dragged down by the surface and there will be a gaping hole in the surface.  Another way to identify these holes is to look at the color palette of the scene and if it does not have the usual distribution of colors – Red to Purple – there is a low point somewhere in the scene.

Low Point in TIN Surface

We can also see the low point using the “Profile” view – it can be seen below the surface.

Low Points Below the Filtered Surface

These points can be re-classified and removed from the Ground Classification and placed into the “Low Point / Noise” Classification and then the surface is modified.  Note the better distribution of the color palette for the scene…

Resulting TIN Surface

Finally, the resulting profile shows the points reclassified to the correct classification.  Repeat for each tile until complete!

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