Translation

  • Convert one format to another

  • Do stuff along the way

Compression

Purpose:
  • Output a compressed LASzip

  • Learn about point cloud metadata

  • Learn about ASPRS LAS

LASzip

  • ASPRS LAS data model

  • Typical 5:1 to 10:1 ratios

  • Incremental, interruptable, and chunkable

  • Unencumbered open source

  • C++ and JavaScript

Command (compression)

1
2
pdal translate ./exercises/translation/interesting.laz \ 
./exercises/translation/interesting.las
  • PDAL chooses option based on filename extension

  • Not all extensions work

  • Imprecise. Use Pipeline if you need to be explicit

Verify (compression)

_images/compression-verify.png

Reprojection

Purpose:
  • Transform data in one coordinate system to another

  • Utilize driver options

  • Scale output data

Reprojection Workshop Materials

Command (reproject)

pdal translate ./exercises/analysis/ground/CSite1_orig-utm.laz \
  ./exercises/translation/csite-dd.laz reprojection \
  --filters.reprojection.out_srs="EPSG:4326"
  • We tell filters.reprojection to output to EPSG:4326

  • Add reprojection filter directly to translate command

  • Define reprojection filter option via command line

Command (bad scale)

_images/reprojection-wrong-scale.png

Command (scale)

pdal translate \
./exercises/analysis/ground/CSite1_orig-utm.laz \
./exercises/translation/csite-dd.laz reprojection \
--filters.reprojection.out_srs="EPSG:4326" \
--writers.las.scale_x=0.0000001 \
--writers.las.scale_y=0.0000001 \
--writers.las.offset_x="auto" \
--writers.las.offset_y="auto"
  • Scale set to 1e-7

  • Offset to auto (PDAL calculates minimum)

Command (verify)

_images/reprojection-proper-scale.png