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Standard "off-the-shelf" digital elevation model (DEM) imagery is processed to serve general purpose mapping purposes — and in that process, subtle karst features are routinely smoothed away. Custom terrain imagery derived directly from raw LiDAR point cloud data can recover that lost detail, and then go further, with tuning specifically aimed at making sinkholes, sinking streams, and other karst topography stand out.
This presentation draws on Kentucky's statewide Phase 2 LiDAR dataset as a working example, though all techniques described are applicable to LiDAR data from any source. Tools covered include ArcGIS Pro (available for personal use at $110/year), as well as the no-cost alternatives LAStools, PDAL, QGIS, and Python.
Topics will include:
- Limitations of standard off-the-shelf terrain imagery
- The value of "Class 7" LiDAR data for karst analysis
- Sources for raw LiDAR surface data
- Toolset options and workflows
- Preserving resolution through the processing pipeline
- Optimizing visual impact using non-standard color ramps, layer blending of elevation, hillshade and slope, and scalable contours (6-inch contour intervals are achievable)
- Techniques for highlighting karst features
- Online hosting
- Integration of finished imagery with 2D and 3D cave survey data from Walls or Compass
Joe Walko