In the continental U.S., is the Geoid above or below the Ellipsoid?

Question

In the continental U.S., do we know if the Geoid for NAVD 88 is above or below the NAD83/GRS 80 Spheroid? Or, do they every criss-cross each other?

...Just a "curious" thing.

With that, I'm wondering about where we have negative elevation values like in Death Valley?

Bojan≈†avriƒç · Answer

Hi @Craig_Eissler_Iceman,

According to the NOAA's National Geodetic Survey website regarding the current GEOID18 model, it appears that geoid heights are all negative for CONUS. This would indicate that the current geoid model for NAVD88 is consistently below the GRS80 ellipsoid for NAD83 (2011).

I hope this helps,
Bojan