Custom Vertical Coordinate System(AHD), AUSGeoid09 Models

NOW EDITED AS RESOLVED

I am setting up our ContextCapture workflow with out new PPK enabled UAV. I am able to get an output but it's not lining up with GCPS or liking the Australian Coordinate Systems (AHD Heights).

Ideally we would fly our mission PPK process the images to be within a cm or 2 process in context and derive our 3D content.

Item 1 Vertical Coordinate system: (RESOLVED)

I'm having some issues creating a custom vertical coordinate system and utilise the more accurate local GEOID model as per the support document and forum posts.

https://communities.bentley.com/products/3d_imaging_and_point_cloud_software/f/contextcapture-descartes-pointools-forum/153294/create-user-defined-system/458045#458045

I have downloaded the appropriate Geoid model(AUSGeoid09_V1.01.gsb). Ausgeoid converts elipsoidal heights to MSL in Australia.
converted it to gtx using the GDAL tools
Added a line for vertcs.csv and can see this in the "override vertical coordinate system"
I was getting the message "This spatial reference system is not adapted to this area" when I try to select "WGS84 and AHD" and the OK button is disabled. NOW RESOLVED this was due to the .gtx file being incorrectly created into a 4 band image.

Now resolved the I Files used:

vertcs.csv

AUSGeoid09_V1.01.gtx

Regards Graham Wood(Newcastle City Australia)

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Offline Oto Wed, Jun 20 2018 9:35 AM in reply to Oto +1 verified

Uploading your GTX file to http://mygeodata.cloud and comparing to my GTX I see there are differences as yours show up as TIF 4-band and not as GTX format(NOAA VDatum binary grid).

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0 Offline Oto Wed, Jun 20 2018 5:18 AM
"This spatial reference system is not adapted to this area" it means that grid is different coordinate system than coordinates. Maybe the GTX is not converted correctly.

Also when using PPK data set aerotriangulation to accurate metadata otherwise could get wrong results - communities.bentley.com/.../460472
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0 Offline Graham Wood Wed, Jun 20 2018 9:07 AM in reply to Oto

Thanks Oto: So Gdal/context capture won't transform the height values unless there is a matching horizontal grid? I'll have to find something that can read the .gsb or .gtx metadata..

I"m starting to think I'll look at scripting the image metadata and control to WGS84 and ellipsoidal heights and use FME at the end to transform into AHD heights.

I have been keeping the position and rotation at Aerotriagulation and letting the camera parameters be flexible. I'm thinking we need to do a calibration flight of something with more surfaces than a football field at multiple angles and heights.
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0 Offline Oto Wed, Jun 20 2018 9:31 AM in reply to Graham Wood
I got such error when wrongly converted our local national geoid grid to GTX format and didn't intechange LatLon values so it resulted in wrong GTX file.

Log a service ticket and ask Bentley if NTV2 GSB grids are also supported without converting. Contextcapture uses GDAL libraries so should be possible.
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+1 Offline Oto Wed, Jun 20 2018 9:35 AM in reply to Oto
Uploading your GTX file to http://mygeodata.cloud and comparing to my GTX I see there are differences as yours show up as TIF 4-band and not as GTX format(NOAA VDatum binary grid).
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+1 Offline Oto Wed, Jun 20 2018 9:35 AM in reply to Oto
Uploading your GTX file to http://mygeodata.cloud and comparing to my GTX I see there are differences as yours show up as TIF 4-band and not as GTX format(NOAA VDatum binary grid).
Answer Verified By: Graham Wood
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0 Offline Graham Wood Wed, Jun 20 2018 9:55 AM in reply to Oto

Interesting I'll try to convert the .gsb file again.
I used this resource

https://github.com/OSGeo/proj.4/wiki/VerticalDatums

GDALInfo returned a similar result

C:\OSGeo4W64\bin\gdalinfo.exe "C:\Users\Woody\Downloads\AUSGeoid09_V1.01.gtx"
Driver: GTiff/GeoTIFF
Files: C:\Users\Woody\Downloads\AUSGeoid09_V1.01.gtx
Size is 3120, 2280
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (107.991666666666660,-7.991666666666666)
Pixel Size = (0.016666666666666,-0.016666666666666)
Metadata:
AREA_OR_POINT=Area
CREATED=01012010
GS_TYPE=SECONDS
MAJOR_F=6378137
MAJOR_T=6378137
MINOR_F=6356752.314
MINOR_T=6356752.314
PARENT=NONE
SUB_NAME=AUSGEOID
SYSTEM_F=GDA94
SYSTEM_T=AHD_1971
UPDATED=01012010
VERSION=1.0.0.0
Image Structure Metadata:
INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left ( 107.9916667, -7.9916667) (107d59'30.00"E, 7d59'30.00"S)
Lower Left ( 107.9916667, -45.9916667) (107d59'30.00"E, 45d59'30.00"S)
Upper Right ( 159.9916667, -7.9916667) (159d59'30.00"E, 7d59'30.00"S)
Lower Right ( 159.9916667, -45.9916667) (159d59'30.00"E, 45d59'30.00"S)
Center ( 133.9916667, -26.9916667) (133d59'30.00"E, 26d59'30.00"S)
Band 1 Block=3120x1 Type=Float32, ColorInterp=Gray
Description = Latitude Offset (arc seconds)
Band 2 Block=3120x1 Type=Float32, ColorInterp=Undefined
Description = Longitude Offset (arc seconds)
Band 3 Block=3120x1 Type=Float32, ColorInterp=Undefined
Description = Latitude Error
Band 4 Block=3120x1 Type=Float32, ColorInterp=Undefined
Description = Longitude Error
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0 Offline Graham Wood Wed, Jun 20 2018 9:59 AM in reply to Graham Wood

running the conversion again returned a single band.

I'll investigate tomorrow at work(thanks for the fresh set of eyes)

Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4326"]]
Origin = (107.991666666666674,-7.991666666666667)
Pixel Size = (0.016666666666666,-0.016666666666666)
Metadata:
CREATED=01012010
GS_TYPE=SECONDS
MAJOR_F=6378137
MAJOR_T=6378137
MINOR_F=6356752.314
MINOR_T=6356752.314
PARENT=NONE
SUB_NAME=AUSGEOID
SYSTEM_F=GDA94
SYSTEM_T=AHD_1971
UPDATED=01012010
VERSION=1.0.0.0
Corner Coordinates:
Upper Left ( 107.9916667, -7.9916667) (107d59'30.00"E, 7d59'30.00"S)
Lower Left ( 107.9916667, -45.9916667) (107d59'30.00"E, 45d59'30.00"S)
Upper Right ( 159.9916667, -7.9916667) (159d59'30.00"E, 7d59'30.00"S)
Lower Right ( 159.9916667, -45.9916667) (159d59'30.00"E, 45d59'30.00"S)
Center ( 133.9916667, -26.9916667) (133d59'30.00"E, 26d59'30.00"S)
Band 1 Block=3120x1 Type=Float32, ColorInterp=Undefined
Description = Latitude Offset (arc seconds)
NoData Value=-88.8888000000000034
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0 Offline Oto Wed, Jun 20 2018 10:08 AM in reply to Graham Wood
As an alternative try to download it from here in txt format - ftp://ftp.ga.gov.au/geodesy-outgoing/gravity/ausgeoid/AUSGeoid09_V1.01.txt

And convert using https://www.eye4software.com/hydromagic/documentation/manual/utilities/geoid-file-conversion/

or if it doesn't work then convert from one of these - https://www.eye4software.com/hydromagic/documentation/geoid-models/
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