[pdal] Regarding Reprojection Between Vertical Datums

[Nicholas Stanley]

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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