Geoid Model Data

G eoid models are used to measure precise surface elevations. The geoid model contributes to the vertical component of the B.C. geospatial reference system so that ellipsoidal Global Navigation Satellite System (GNSS) heights can be converted to orthometric elevations for practical uses.

The geoid is roughly equivalent to mean sea level plus the natural continuation of mean sea level under the landmass. This extension must be modelled or determined mathematically. The geoid model is actually based on precise levelling to monuments where GNSS heights have been observed, as well as gravity data collected worldwide. Once the geoid is determined, the difference between the two surfaces, the ellipsoid and the geoid, can be computed. This difference is known as geoid-ellipsoid separation, or geoidal height.

A precise geoid model allows the user to compute orthometric or sea-level elevations using GNSS technology anywhere across the country.

Metro Vancouver Geoid

A precise geoid model that covers all of Metro Vancouver (MV), Abbotsford and east to Hope is available for download. This geoid model is loaded into Management of Survey Control Operations & Tasks (MASCOT) for all geodetic control monuments in MV, ensuring that MASCOT and the Real Time Kinematic service are completely compatible.

The official name of the geoid model being distributed is HTMVBC00. It has been renamed to ensure that users are employing the correct model. This model is equivalent to HTGVRDBC00, except it is extended to the east to provide coverage for Abbotsford:

The BYN file above can be directly imported into GPS software. Natural Resources Canada provides GPS-H, a tool that can view and extract geoid values from BYN files.