What is the model of the Earth used by VBOX devices?

The Geodetic datums, or models of the earth, that the VBOX GPS engines use are the WGS 84 (ellipsoidal) or the EGM 96 (geoidal).

These are recognised standard models of the shape of the earth. Referencing geodetic coordinates to the wrong datum can result in position errors of hundreds of meters. Different nations and agencies use different datums as the basis for coordinate systems used to identify positions in geographic information systems, precise positioning systems, and navigation systems.