GRS80 ellipsoid heights to NGVD88 elevations. Anyone know of a website or software package?
Geoid96 should do the trick.
From the NGS "The National Geodetic Survey has developed a program, GEOID96, which models the separation between the GRS80 ellipsoid and NGVD88 across the U.S."
Geoid09 at the NGS website.
SHG
ellipsoid heights to orthometric heights
Howdy,
You need to be more specific. If h is ellipsoid height, H is orthometric height and N is the ellipsoid-geoid separation,
then h - h - N = 0.
The important thing to note is that an ellipsoid height must be associated with a particular datum or realization. Look at an OPUS solution, there are two ellipsoid heights shown. These heights differ and cannot be mixed in the above equation. Here in S Texas h differs between NAD83 and ITRF08 by about 1.3 meters.
IF I have an NAD83 ellipsoid height and want an NAVD88 orthometric height, I would use the most recent NGS hybrid geoid model. NGS names its hybrid models GEOID with the year the model is computed/released. I understand that GEOID2012 is nearly complete and should be released soon. The NGS hybrid model is based on a gravimetric model (called USGG) with the addition of datum transformations as well as a "corrector surface" derived from a data set consisting of GPS observations (yielding ellipsoid heights) on NAVD88 benchmarks (Helmert orthometric heights).
IF I have an ITRF08 ellipsoid height and want to derive an orthometric height then the model to use is the current version of USGG. The US and Canada are moving toward new vertical datum be based on gravimetric geoid models. I also understand Mexico is planning a similar move.
GRS80 is a reference ellipsoid. It is the reference ellipsoid associated with ITRF and NAD83 as well as other national datums. I can transform Earth Centered Earth Fixed (ECEF) coordinates (XYZ) to latitude, longitude and ellipsoid height using GRS80 parameters.
Ellipsoid heights are measured with respect to the reference ellipsoid. Orthometric heights are measured with respect to the geoid. "Geoid heights" are the distance from the reference ellipsoid to the geoid.
I imagine the reference to NGVD88 was a mistake as the current US national vertical datum is North American Vertical Datum of 1988 (NAVD88).
Hope this helps,
DMM
ellipsoid heights to orthometric heights
Nice reply! I typed my short reply earlier on my phone 🙂
SHG
ellipsoid heights to orthometric heights
Excellent response. :good: :good:
Geoid12 is supposed to be released today, Saturday.
I haven't checked, though to see if they did release it today.
Geoid12 is supposed to be released today, Saturday.
Yup...
I noticed it this morning. Herre's a link:
http://www.ngs.noaa.gov/GEOID/GEOID12/
It appears to be still be "under construction" at this point though.
Loyal
Geoid12 is supposed to be released today, Saturday.
Thanks for the link.
Geoid12 interactive tool available now
Howdy,
The interactive Geoid2012 tool at
http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/geoid12_prompt1.prl
seems to be working.
Enjoy,
DMM
Geoid12 is supposed to be released today, Saturday.
Stuff seems to ALWAYS be under construction. 🙂
Geoid12 interactive tool available now
Thanks for the link!!!
Geoid12 is supposed to be released today, Saturday.
Thanks to everyone who replied. This is an awesome community.
Geoid12 is supposed to be released today, Saturday.
They would've finished it except...well, my Attorney advises me to not talk about ;-).
