GEOM
Credits Data sources & licences
Where the numbers come from.
GEOM does not work out Belgian coordinates on its own authority. It applies grids and models that other people built, tested and published. Two of them are licensed CC BY 4.0, so crediting them here is a condition of use rather than a courtesy.
- Horizontal grid
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BD72 / Lambert 72 ↔ ETRS89 / Lambert 2008
be_ign_bd72lb72_etrs89lb08.tif: © 2014–2016 Nicolas Simon, validated and distributed by NGI/IGN Belgium (Nationaal Geografisch Instituut / Institut géographique national). Licensed CC BY 4.0. This grid carries the internal distortion of BD72, which a seven-parameter Helmert cannot represent. That is why GEOM insists on having it. - Vertical grid
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Ellipsoidal height ↔ mTAW
be_ign_hBG18.tif: Slobbe, Klees, Farahani, Huisman, Alberts, Voet, De Doncker (2018), The Belgian hybrid quasi-geoid hBG18 V.1.0, GFZ Data Services, DOI 10.5880/isg.2018.003. Derived from work by IGN Belgium. Licensed CC BY 4.0. A quasi-geoid returning normal heights, which is what mTAW is. - RTK corrections
- Any NTRIP caster GEOM connects to any NTRIP caster you hold an account with, entering the host, port, mountpoint and login yourself. No correction data and no credentials are shipped with GEOM.
- Projection engine
- PROJ 9.6.0 MIT/X-style licence, bundled and version-pinned. Includes the EPSG Dataset, which remains subject to the terms of use of the IOGP Geomatics Committee. GEOM runs PROJ with network access disabled and ballpark transformations forbidden.
- Reference data
- NGI cConvert · MercatorNet GEOM's coordinate engine is validated against transformation results from NGI cConvert and the MercatorNet test dataset published by Departement Omgeving, Vlaamse overheid. Neither is derived from PROJ, which is what makes the comparison worth running.
- Basemaps
- OpenStreetMap · CARTO · Esri Map data © OpenStreetMap contributors, licensed ODbL. The browser's dark theme draws its street basemap from CARTO, credited in the map whenever those tiles are on screen. Satellite and hybrid imagery via Esri ArcGIS World Imagery. Drone orthophotos are streamed from the source you point GEOM at, never copied onto our servers.
- Libraries
- MapLibre GL JS · three.js · proj4js · GRDB · libtiff MapLibre GL JS is BSD-3-Clause. three.js and proj4js are MIT. proj4js is used only for grid-free projections in the browser; the grid-based Belgian datum transforms are never computed by it.
- Hardware
- Emlid Reach RX2 Emlid, Reach and Reach RX2 are trademarks of Emlid. GEOM is an independent third-party application built on Emlid's public documented streaming interface. It is not an Emlid product, and it is not endorsed by Emlid. Apple, iPhone and MFi are trademarks of Apple Inc.