[pdal] proper syntax for applying a geoid in newer versions

[Jeff Bourdier]

Instead of "+init=EPSG:32611" or "+proj=utm +zone=11 +type=crs", you might
try the fully expanded PROJ string
<https://spatialreference.org/ref/epsg/32611/proj4/>:

+proj=utm +zone=11 +ellps=WGS84 +datum=WGS84 +units=m +no_defs


So your pipeline would be:

*{"pipeline": [{"type" : "readers.las",*
*                  "filename": "input_Ellipsoidal.laz"},*
*                 {"type":"filters.reprojection",*
*                  "in_srs":"EPSG:32611",*
*                  "out_srs":"*+proj=utm +zone=11 +ellps=WGS84 +datum=WGS84
+units=m +no_defs* +geoidgrids=g2003conus.gtx"},*
*                 {"type" : "writers.las",*
*                  "filename": "output_Geoid.laz",*
*                  "compression": "laszip",*
*                  "a_srs": "EPSG:32611+5703"*
*                 }]}*



On Fri, Apr 28, 2023 at 10:09 AM Matt Beckley <matt.beckley at earthscope.org>
wrote:

> Hello,
>
> In older versions of PDAL I used to be able to run a pipeline like:
>
> *{"pipeline": [{"type" : "readers.las",*
> *                  "filename": "input_Ellipsoidal.laz"},*
> *                 {"type":"filters.reprojection",*
> *                  "in_srs":"EPSG:32611",*
> *                  "out_srs":"+init=EPSG:32611
> +geoidgrids=g2003conus.gtx"},*
> *                 {"type" : "writers.las",*
> *                  "filename": "output_Geoid.laz",*
> *                  "compression": "laszip",*
> *                  "a_srs": "EPSG:32611+5703"*
> *                 }]}*
>
>
> This would run fine, and the output would have the geoid properly applied.
>
> However, newer versions of PDAL (e.g. 2.5.3) uses newer version of PROJ,
> which no longer likes its string in the form, "+init=epsg:XXXX".  It will
> give the warning:
> "Warning 1: +init=epsg:XXXX syntax is deprecated. It might return a CRS
> with a non-EPSG compliant axis order."
>
> I adjusted the PROJ string to remove this convention:
>
> *{"pipeline": [{"type" : "readers.las",*
> *                  "filename": "input_Ellipsoidal.laz"},*
> *                 {"type":"filters.reprojection",*
> *                  "in_srs":"EPSG:32611",*
> *                  "out_srs":"*+proj=utm +zone=11 +type=crs
> * +geoidgrids=g2003conus.gtx"},*
> *                 {"type" : "writers.las",*
> *                  "filename": "output_Geoid.laz",*
> *                  "compression": "laszip",*
> *                  "a_srs": "EPSG:32611+5703"*
> *                 }]}*
>
> This runs without warning or errors, but the output grid *does not* have
> the geoid applied.  Most of the documentation on this type of operation
> I've seen still refers to the older PROJ syntax of, "+init=epsg:XXXX".
>
> Is there a way to apply a geoid with the new PROJ syntax, and hopefully I
> am just missing something with the proper syntax to do this operation on
> the newer versions of PDAL?
>
> Thanks!
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