Vertical grid shiftΒΆ

Change Vertical datum change by grid shift

Input type

Geodetic coordinates (horizontal), meters (vertical).

Output type

Geodetic coordinates (horizontal), meters (vertical).

Options

+grids

Comma-separated list of grids to load.

The vertical grid shift is done by offsetting the vertical input coordinates by a specific amount determined by the loaded grids. The simplest use case of the horizontal grid shift is applying a single grid. Here we change the vertical reference from the ellipsoid to the global geoid model, EGM96:

+vgridshift +grids=egm96_16.gtx

More than one grid can be loaded at the same time, for instance in the case where a better geoid model than the global is available for a certain area. Here the gridshift is set up so that the local DVR90 geoid model takes presedence over the global model:

+vgridshift +grids=@dvr90.gtx,egm96_16.gtx

The @ in the above example states that the grid is optional, in case the grid is not found in the PROJ search path. The list of grids is prioritized so that grids in the start of the list takes presedence over the grids in the back of the list.

PROJ supports the GTX file format for vertical grid corrections. Details about all the format can be found in the GDAL documentation. GDAL both reads and writes the format. Using GDAL for construction of new grids is recommended.