Reprojection¶
Exercise¶
This exercise uses PDAL to reproject ASPRS LAS data
Issue the following command in your Docker Quickstart Terminal.
1 2 3 4 5 | docker run -v /c/Users/Howard/PDAL:/data -t pdal/pdal \
pdal translate /data/exercises/analysis/ground/CSite1_orig-utm.laz \
/data/exercises/translation/csite-dd.laz \
reprojection \
--filters.reprojection.out_srs="EPSG:4326"
|

Unfortunately this doesn’t produce the intended results for us. Issue the following
pdal info
command to see why:
docker run -v /c/Users/Howard/PDAL:/data -t pdal/pdal \
pdal info /data/exercises/translation/csite-dd.laz --all

Some formats, like writers.las do not automatically set scaling
information. PDAL cannot really do this for you because there are a number
of ways to trip up. For latitude/longitude data, you will need to set
the scale to smaller values like 0.0000001
. Additionally, LAS uses
an offset value to move the origin of the value. Use PDAL to set that
to auto
so you don’t have to compute it.
1 2 3 4 5 6 7 8 9 10 | docker run -v /c/Users/Howard/PDAL:/data -t pdal/pdal \
pdal translate \
/data/exercises/analysis/ground/CSite1_orig-utm.laz \
/data/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"
|

Run the pdal info command again to verify the X
, Y
, and Z
dimensions:

Notes¶
- filters.reprojection will use whatever coordinate system is defined
by the point cloud file, but you can override it using the
in_srs
option. This is useful in situations where the coordinate system is not correct, not completely specified, or your system doesn’t have all of the required supporting coordinate system dictionaries. - PDAL uses proj.4 library for reprojection. This library includes the capability to do both vertical and horizontal datum transformations.