Point Cloud Options

Points clouds are a category of GIS data.  This forms allow manipulation of the LAS point cloud.

Tabs provided detailed option selection:
  • General
  • File list
  • Tools
  • Stats
  • Draw
  • Create grids  Create a new grid that matches the DEM covering the map.
  • Filter
Main controls on the bottom of the form, always visible:
  General tab. 

Thinning for OpenGL, and slices

KML vertical offset, to put the points above the landscape. 

Files list tab.  List of files to be used.
  • LIB Add all indexed files from Map library included on this map. Auto load from the Map library set on the Indexes tab of the options form, automatically adds files when the form opens.
  • Metadata: Display Metadata for the files. If there are a lot of files, you probably only want to look at a few.
  • Outline tiles on the current map
  • Zoom: restrict map to just area covered by the point cloud.
  • On Map: do not open tiles that are not on the map.  If you zoom out, they will not automatically appear.
  • Label: Label the tiles.  You might have to adjust the map colors to see them.
  • Add #1, #2, #3, #4 Pick individual files/directories to included.  You can open multiple point clouds, and turn them on and off rapidly.
Tools tab:  Many of these options require that the base map in use have a DEM associated with it, which will determine the size of the grid created.

Point based

  • Extract map LAS, Extract masked, Extract valid grid:
    • Extract points on the current map, which might be in multiple files, into a single LAS file or 3D shapefile.  Pick a small map area for this option.
    • For mask option, the current map must have a mask in red, and only points that project to a red pixel on the map will be extracted.
    • For extract valid grid, only points that map to valid values in the DEM associated with the map will be extracted.
  • Extract GeoJSON: for current map area, create file
  • Points above DEM, Points below DEM: puts the points above or below the DEM on the map into the memo box on the right of the form.  This uses the Zcrit defined below.

Zcrit: buffer added to DTM before deciding if point is not on the ground.


DEM Z:

  • Interpolate: get elevation with a bilinear interpolation.
  • Floor/ceiling: get elevation from highest or lowest, as appropriate, of the 4 grid nodes surrounding the point cloud location.  This can be better in regions of steep slope in the DEM.

 

Stats tab:

  • Histograms/Counts: histograms for elevation and intensity, and a count of the returns in each category, and by return number.
  • Zero classification: merge all LAS files in the current files listing into a single file, with the classifications all reset to zero.
  • Reclassify:
  • Split by class: create new files by classification (vegetation, buildings, ground, non_ground, unclassified, and other)
  • Recenter files: recenter all coordinates so that multiple files share the same values.  This is designed for use with Cloud Compare, and not at this time to create usable LAS files for further analysis.
  • Subset/tile: recursively quarter files until all file sizes are under a specified value;
  • Zero fields : set the following fields to zero: Intensity, ReturnFlags, ScanAngle, UserData, PointSourceID
  • Ground point classification

Compare two point clouds

Other Point Cloud Viewers and Lidar tools

Lidar Point Cloud Data Sources

File prep and work flow to create grids

Problems with point clouds


Last revision 1/7/2018