Are negative values allowed for ADAS Absolute Height?

Are negative values allowed for ADAS Absolute Height?

Examples in NA, Florida 27.950324185955257, -82.45113675582347



Yes, this is possible.

WGS84 which is used as a reference system for the GPS uses a reference ellipsoid – a mathematically defined surface (a model) that approximates the geoid.

While the geoid itself - as a real physical shape of the Earth, or rather the ocean surface of the Earth extended through the continents – is an irregular surface, due to the uneven distribution of mass within Earth and on its surface. The geoid undulation deviates from +85m (Iceland) to -106m (southern India). Please see the visualization on: https://en.wikipedia.org/wiki/Geoid#/media/File:Earth_Gravitational_Model_1996.png



The examples above case are in Florida, so in the range between -40 and -20m, according to the picture above.

And using some special ellipsoid to geoid calculator we can see that for the lat/lon provided the real geoid height is -26,78m. In other words there is a geoid dip in that area.