Using free and/or open source tools to build workflows to manipulate and process LiDAR data

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Using free and/or open source tools to build
workflows to manipulate and process LiDAR data

• Christopher Crosby

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Point cloud filtering (classification)
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Software options for point cloud filtering

• ALDPAT - http//mitigation.fiu.edu/lidartool.html
• Open source option for full LiDAR workflow
• Task 1. Split Tape Files into Strips
• Task 2. Separate First and Last Return
  Measurements from a 9 Column Strip File
• Task 3. Convert ellipsoid to orthometric heights
• Task 4. Estimate strip boundary
• Task 5. Merge Boundary Files
• Task 6. Create Shape File
• Task 7. Tile Strips
• Task 8. Filter LIDAR Points
• Task 9. Gridding Tiles
• Task 10. Convert Surfer Grids to ArcGIS Grids
• Miscellaneous Tasks
• Very linear output of one task is input for
  following task

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ALDPAT filtering algorithms

• Elevation Threshold with Expand Window (ETEW)
• Progressive Morphology (PM)
• 2D Morphological Filters (Square or Circle Window
• Maximum Local Slope (MLS)
• Iterative Polynomial Fitting (IPF)
• Polynomial Two-Surface Filter
• Adaptive TIN (ATIN)
• Refer to users guide for description and
  parameters for each

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Software options for point cloud filtering

• ArcGIS 3rd Party Extensions
• Qcoherent LP360 - http//www.qcoherent.com/
• VLS LiDAR Analyst - http//www.featureanalyst.com/
  lidar_analyst.htm
• 1k / seat (academic)
• Industrial Solution
• TerraSolid Software suite - http//www.terrasolid.
  fi/en/products/4
• 10k - 30k depending upon bundle

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Game plan

• Convert LAS point data to ASCII - LASTools
• Grid ASCII points Points2Grid
• Experiment with search radius and gridding
  parameters
• Visualize results ArcGIS or Global Mapper
• Grid file format conversions and projection - GDAL

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Tools

• LasTools (point cloud format conversions)
• GEON Points2Grid (DEM generation)
• GDAL w/ discussion of EPSG (Raster data
  conversion and projection)
• ALDPAT (point cloud filtering) time and
  complexity doesnt permit full discussion

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MS-DOS Commands

• Run gt cmd to get command line window
• Basic Navigation
• cd directory - go into directory
• cd .. - up a directory
• cd ../.. up two directories
• dir to list contents of a directory
• help command - lists flags and usage
• exit -
• TAB auto complete

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LAStools

• http//www.cs.unc.edu/isenburg/lastools/
• Martin Isenburg, Jonathan Shewchuk - UNC
• converting, viewing, and compressing LIDAR data
  in LAS format
• MS-DOS command line tools

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GEON Points2Grid

• Desktop application to generate DEMs and shot
  density plots from LiDAR point cloud data.
• Same algorithm as available in the GEON LiDAR
  Workflow system online
• Algorithm by Han Kim (UCSD)
• Windows implementation by Newton Alex (ASU)

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http//lidar.asu.edu/points2grid.html
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GDAL - Geospatial Data Abstraction Library

• is a translator library for raster geospatial
  data formats that is released under an X/MIT
  style Open Source license by the Open Source
  Geospatial Foundation
• http//www.gdal.org/
• Very powerful tool for raster file conversions
  and projection.
• Available for Linux, Mac, Windows
• Recommend installing full FWTools package which
  includes GDAL http//fwtools.maptools.org/
• Open Source GIS Binary Kit for Windows and Linux

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EPSG

• Numeric codes that refer to a specific coordinate
  system. Used by software such as GDAL to define
  projection.
• http//spatialreference.org/

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http//lidar.asu.edu/LViz.html