I have a series of lidar-based raster products created via FUSION. Since I am working with low density lidar data, many of the raster images show significant striping where lidar returns overlap on the borders of the flight lines (displayed as red lines). I need to automatically detect and list these striped rasters for quality control purposes. What methods can I use to automatically check these rasters for the striped effect shown in the attached image?

enter image description here

  • I create a raster on a 5m cell and count the number of first returns - exclude counts of 0 and raster to polygon. This is a reasonable guide but for your purposes you might want to go 10m or more on the cell size and overlay the strips to find just the overlap areas. If you are using ArcGis you can make a lidar dataset (from 10.1) and convert to raster (intensity perhaps) using LAS Dataset To Raster resources.arcgis.com/en/help/main/10.2/index.html#//…. There is another method using 'edge of flight line' markers in the las file but that is not 'off the shelf'. – Michael Stimson Apr 27 '14 at 22:44

You can try 'lasoverlap.exe' to quickly both visualize and quantify the overlap. And you can use 'lasoverage.exe' to remove the extra layers when there is overlap among points based on the scan angle. Both these modules are part of LAStools, which come with a toolbox for both ArcGIS and QGIS. Attached is a visualization of an example visualization produced by 'lasoverlap.exe' ...enter image description here

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    If there is a discrepancy in intensity from one flight path to the next, lasoverage will eliminate the overlapping points, but leave behind a "lip" (a jump in intensity value) along the flight path edge, right? Do you know of any free tool that could "fit" the flight paths to their neighboring flight paths (based on the overlapping points), to remove this "lip"? (I don't care if the result is not physically accurate - I just need a terrain output without visual artifacts in the heights.) – ToolmakerSteve Apr 16 '17 at 4:43
  • To automatically adjust the intensity values of neighboring flightlines is a tricky task. There are also "normalized reflectivity" values that you can use instead of the default (not properly defined) intensity values if your vendor is operating a RIEGL scanner. There is a method developed at Ryerson University by the team of Dr. Ahmed Shaker that looks quite promising. For another (much simpler) approach look at this blog post here: rapidlasso.com/2016/04/05/… – LAStools Apr 17 '17 at 14:58

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