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

[Michael Smith]

Rather than a proj string, it would be better to use WKT2 or PROJJSON. You should use projinfo to generate the output srs. 

 

Mike

 

 

-- 

Michael Smith

US Army Corps / Remote Sensing GIS Center

 

 

 

From: pdal <pdal-bounces at lists.osgeo.org> on behalf of Jeff Bourdier <jeffbourdier at gmail.com>
Date: Friday, April 28, 2023 at 3:24 PM
To: pdal <pdal at lists.osgeo.org>
Subject: Re: [pdal] proper syntax for applying a geoid in newer versions

 

Instead of "+init=EPSG:32611" or "+proj=utm +zone=11 +type=crs", you might try the fully expanded PROJ string:

 

+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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