Wednesday, December 8, 2010

LidarViewer and Projected Coordinates

For Structural Geology lab, we were instructed to use the open sourced LidarViewer to measure strike and dips on a LIDAR point cloud of Raplee Ridge.  LidarViewer relies on an open sourced library and GUI called Vrui.  Both are products of UC Davis.

LidarViewer uses Vrui to display the LIDAR point cloud in 3D.  Vrui uses WGS 84 as its geodetic coordinate system.

Oddly, I cannot figure out what that PCS is.  It looks like a Mercator given the magnitude of the units.  Yet, the eastings and northings always mismatches the various projections found in QGIS.  World Mercator?  Nope.  At times it seemed rather non-linear.

Does anyone know what the heck Vrui is doing to get its 2D coordinates?  It is using WGS 84, so a false easting and northing would be nice to have...

I attempted understanding the code, but Vrui, being C++ code, is so abstracted that I can't make heads or tails of what is going on (I profess my love of Python!).  Perhaps it is taking whatever the projection was of the LIDAR point cloud?  If so, then the Raplee Ridge data has a very odd projection.  At least, odd in that I can't find a good match for it.

Knowing what the PCS is would be helpful in the future: I could take strike and dips plus have the coordinates saved to a file.  I like efficiency.

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