[pdal] Regarding Reprojection Between Vertical Datums
Nicholas Stanley
nicholas.stanley at luminartech.com
Tue Jul 12 14:12:49 PDT 2022
Thanks,
Yes, that was an oversight in respect to the +4326 - thanks.
To reiterate:
I am trying to get the /NAD83(2011) / Conus Albers + NAVD88 height/ data
*out* of its native elevation model, converted *into* a wgs84 EPSG 32610
ellipsoidal projection.
When I run the conversion command / //pdal translate filename.laz
filename_utm.laz reprojection --filters.reprojection.out_srs="EPSG:32610"//
/The resulting file lines up in Easting/Northing precisely, but seems to
have retained the old elevation data (which is ~30M+ above our UTM10
WGS84 "Ground Truth")
On 7/12/22 14:03, Jim Klassen wrote:
>
>
> On 7/12/22 15:41, Nicholas Stanley wrote:
>>
>> Greetings,
>>
>> My goal is to reproject/align a third party GRS80 point cloud data
>> source to an existing UTM10 WGS84 (EPSG 32610) georeferenced point
>> cloud file/"ground truth".
>>
>> Running Lasinfo on the third party data source (to be
>> corrected/reprojected/aligned to Ground Truth) shows the following:
>>
>>
>> /// 'OGC Transformation Record'//
>> // WKT OGC COORDINATE SYSTEM://
>> // COMPD_CS["NAD83(2011) / Conus Albers + NAVD88
>> height",PROJCS["NAD83(2011) / Conus
>> Albers",GEOGCS["NAD83(2011)",DATUM["NAD83 (National Spatial Reference
>> System 2011)",SPHEROID["GRS
>> 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","1116"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","6318"]],PROJECTION["Albers_Conic_Equal_Area"],PARAMETER["standard_parallel_1",29.5],PARAMETER["standard_parallel_2",45.5],PARAMETER["latitude_of_center",23],PARAMETER["longitude_of_center",-96],PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["meter",1,AUTHORITY["EPSG","9001"]],AXIS["X",EAST],AXIS["Y",NORTH],AUTHORITY["EPSG","6350"]],VERT_CS["NAVD88
>> height",VERT_DATUM["North American Vertical Datum
>> 1988",2005,AUTHORITY["EPSG","5103"]],UNIT["meter",1,AUTHORITY["EPSG","9001"]],AXIS["Up",UP],AUTHORITY["EPSG","5703"]]]
>> ///
>>
>>
>> I am able to successfully reproject the file in PDAL so that the
>> relative 2D alignment in Easting/Northing is corrected - using a
>> command like this:
>>
>> ///pdal translate filename.laz filename_utm.laz reprojection
>> --filters.reprojection.out_srs="EPSG:32610"///
>>
>>
>> *Reviewing the output, this shows proper 2D Grid alignment between
>> ground truth and third party data, but a delta of ~30M in elevation
>> between the ground planes. **This needs to be rectified.
>> *
>>
>> *I've recently found this site describing a process to reproject a
>> .las file in respect to various vertical datums.*
>>
>>
>> http://www.gadom.ski/2017/05/31/vdatum-with-pdal.html
>>
>> ///In order to use//PDAL <https://www.pdal.io/>//to convert vertical
>> coordinates to a new vertical datum, we’ll need to fetch the
>> appropriate geoid. PDAL uses//proj.4 <http://proj4.org/>//under the
>> hood, and proj.4 accepts geoid’s in NOAA VDatum’s//|gtx|//file
>> format. We can fetch the 12B geoid from the//VDatum download website
>> <https://vdatum.noaa.gov/download.php>//. Inside the 12B zipfile
>> there is a file called//|g2012b_conus.gtx|//; this is the geoid for
>> the Continental United States (CONUS). We’ll use this file to convert
>> our data.///
>>
>>
>> I've downloaded the VDatum collection as stated - That said, I've
>> been unable to get the process to work properly.
>>
>> ///pdal translate filename.laz filename_utm.laz reprojection
>> --filters.reprojection.out_srs="+init=EPSG:32610
>> +geoidgrids=~/Downloads/vdatum/g2012b_conus.gtx"
>> --writers.las.a_srs=EPSG:32610+4326//
>> //(pdal translate Error) GDAL failure (1) SetCompoundCS() fails,
>> vertical component is not VERT_CS.//
>> //(pdal translate writers.las Error) GDAL failure (1) PROJ:
>> proj_crs_get_coordinate_system: Object is not a SingleCRS///
>>
>>
>> Does anyone have any Tips/Pointers as to how to resolve/debug this
>> issue?
>>
>> Thanks.
>>
>>
>> _______________________________________________
>> pdal mailing list
>> pdal at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/pdal
>
>
> --writers.las.a_srs=EPSG:32610+4326
>
> There may be more going on here, but "+4326" is likely not correct.
> You need a vert_cs, something like 5703, there. 4326 is a horizontal
> CS. I'm not sure if there is a way to explicitly state you want
> ellipsoid heights. In my experience that's the default if a separate
> vertical component isn't given./
>
> /Also if you have recent PDAL built against recent PROJ (6+) you
> probably want to pull the TIFF files from cdn.proj.org (instead of
> gtx) for the vertical datum conversion./
>
> /
>
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