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OSGeo / PROJ-data

Repository for proj datum grids (for use by PROJ 7 or later)
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Add Chart datum Norway vertical grid. #76

Closed himsve closed 2 years ago

himsve commented 2 years ago

This is the grid with vertical shifts for the transformation from ETRS89 ell. heights to Chart Datum Norway depths.

As I can see from https://github.com/OSGeo/PROJ/tree/master, the transformation by grids from ellipsoidal heights to ortometric depths is not yet solved (regarding the new method code EPSG:1110: https://github.com/OSGeo/PROJ/blob/78eee957b0eff8b74df8a1f0e60a95355e7fa1c6/src/iso19111/operation/transformation.cpp#L2013).

The transformation from from ETRS89 ell. heights to CD Norway depths (EPSG:4937>EPSG:9672) is temporary solved in a personal branch of Proj: https://github.com/himsve/PROJ/commits/typo_cdnorway. The branch is only workaround for internal use and would not be pull requested.

There is also an issue in Proj where the transformation method above is discussed: https://github.com/OSGeo/PROJ/issues/2739

rouault commented 2 years ago

The Computed Min/Max=-959.493,45.875 reported on the dataset looks strange to me. The max value seems consitent of the geoid ondulation of no_kv_href2008a.tif, but -959 is suspicious to me

himsve commented 2 years ago

@rouault Yes, I have seen the strange values in edge of the grid. The values are adopted from the original GravSoft bin file.

But, if you like, it is an easy job for me the remove extreme values in the grid.

rouault commented 2 years ago

But, if you like, it is an easy job for me the remove extreme values in the grid.

Perhaps better if not too complicated. %y remark was just to make sure nothing wrong had happened

himsve commented 2 years ago

The grid is cleaned in the last commit.