NGS Geoid Calculator

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GNSS & Geodesy

Last Post by ease 12 years ago

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ease

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When using this tool to convert from ellipsoid height to geoid height:

https://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/geoid12_prompt1.prl

The data returned is simply a negative number, which I'm assuming is the amount of meters the ellipsoid is below the GEOID? This would agree with the topo maps I have in the area, but why make the results so arcane? I understand it's the gov, but still.

Posted : April 16, 2014 2:30 pm

loyal

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Actually...The 'N' Value is the "distance" (in meters) FROM the Ellipsoidal Surface TO the Geoidal Surface. So a negative 'N' value, tells you that the Geoid is BELOW the Ellipsoid (Ortho Height GREATER than Ellipsoid Height).

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Posted : April 16, 2014 2:37 pm

jered-mcgrath-pls

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> Actually...The 'N' Value is the "distance" (in meters) FROM the Ellipsoidal Surface TO the Geoidal Surface. So a negative 'N' value, tells you that the Geoid is BELOW the Ellipsoid (Ortho Height GREATER than Ellipsoid Height).
>
> Loyal

:good:

Posted : April 16, 2014 2:48 pm