Comments (6)
I can fix the README and try to explain more clearly the reason of additional error appearing if necessary.
yes, that would be helpful if you could separate the accuracy of the official transformation as provided by Ordnance Survey, from the addition error added by using the PROJ grid.
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Can you expand a bit more the text ? I'm not clear what issue you are reporting. See #25 (comment) for more details about creation of this grid
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Yes, this confirms itβs a minor error in the readme file for the grid. Max error is written as 0.02m but should be 0.002m.
Will get around to trying the grid one day.
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@and-marsh uk_os_README.txt mentions: "will agree on average to better than 0.1m (0.1m rmse, 68%
probability).". It seems that this is pessimistic compared to your findings at #25 (comment) .
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@SilverSloth @rouault yes, that's a mistake in the README, of course max error should be 0.002m. But that's an error of reprojection not transformation. I checked that orthometric height obtained by reprojected geoid file matches with results of original transformation, provided by Ordnance Survey. So that RMSE must be taken into account along with the stated error of the original transformation.
In accordance to the EPSG registry coordinate transformation ETRS89 to ODN height (1), code: EPSG::10021 has accuracy 0.02m. So, using reprojected geoid additional error 0.002m can appear.
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I can fix the README and try to explain more clearly the reason of additional error appearing if necessary.
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Related Issues (20)
- Python error trying to run grid_tools/vertoffset_grid_to_gtiff.py HOT 1
- Include EPSG:23700 HOT 4
- Add GCG2016 geoid to support DHHN2016 HOT 6
- Add GSD95 Geoid Model from ca_nrc HOT 2
- Geoid models FIN2000 and FIN2005N00 HOT 3
- Add NGA EGM 2008 1x1 grid_alternative entry HOT 25
- naptrans2018.gtx has alternative grid - nl_nsgi_naptrans2018.tif which is missing from ProjData cdn HOT 4
- 8.0.0: test suite is failing HOT 1
- UK vs GB? HOT 6
- British Columbia grids can be used
- EPSG:2169 conversion issue HOT 1
- Provide github release for proj-data 1.7
- Acceptable licenses and spdx.org/licenses/
- STAC catalog entries for data? HOT 2
- How do we deal with organisations changing names? HOT 4
- Failing Docker image due to SHA256 mismatch on 'no_kv_README.txt' with 'pyproj sync --all' step HOT 2
- PROJ 6 request - OSGM15_GB.gtx HOT 3
- proj-data is packaged incorrectly for cross-platform usage on Debian HOT 3
- https://cdn.proj.org response headers in case of CORS HOT 18
- https://cdn.proj.org response headers are missing in case of CORS HOT 3
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