This repo contains orthometric (geoidal) datum tables in GTX format for geoid models used in Ireland and Sweden.
The files are:
| GTX file | Geoid Model |
|---|---|
| OSGM15_Malin.gtx | OSGM15 Malin Head datum |
| OSGM15_Belfast.gtx | OSGM15 Belfast datum |
| SWEN17_RH2000.gtx | RH2000 |
These tables can be used together as input to proj4 utilities to derive orthometric heights in the respective geoid models.
For example convert WSG84 coordinate to OSGM15 (Malin Head datum) height following command can be used:
echo "-9.45 54.15 95.22" | cs2cs +init=epsg:4326 +to +init=epsg:2157 +geoidgrids=./OSGM15_Malin.gtx
To covert WSG84 coordinate to RH2000 height:
echo "14.72 59.36 100.0" | cs2cs +init=epsg:4326 +to +init=epsg:5845 +geoidgrids=./SWEN17_RH2000.gtx
The above commands assume that proj4 command line utilities are installed and that *.gtx files are located in the current directory.
The GTX files are derived from the source files provided by Ordnance Survey and Lantmäteriet.
| GTX file | Source File | Source Archive |
|---|---|---|
| OSGM15_Malin.gtx | OSGM15_Malin.gri | https://www.ordnancesurvey.co.uk/docs/gps/OSTN15-OSGM15_DevelopersPack.zip |
| OSGM15_Belfast.gtx | OSGM15_Belfast.gri | https://www.ordnancesurvey.co.uk/docs/gps/OSTN15-OSGM15_DevelopersPack.zip |
| SWEN17_RH2000.gtx | SWEN17_RH2000.txt | https://www.lantmateriet.se/globalassets/kartor-och-geografisk-information/gps-och-matning/geodesi/transformationer/swen17_rh2000_txt.zip |
The files were converted with gri2gtx.py python 3 script, in this repository. See the Makefile for details how to run the conversion script.