Trying to convert dem data with ellipsoidal height to orthometric height.
Hi, You need a geoid model that shows the difference (local) between the ellipsoid and the orthometric height system.
There are global models - I use this in Finland
https://www.maanmittauslaitos.fi/en/research/interesting-topics/geoid
I Just add 18.67 m or 18.99 m to my ellipsoidal heights (at 62N, 24E) depending on the height system, which in Finland are renewed every now as Earth's crust is returning its per Ice age shape. I use 18.67 m for 1960 epoch (so called N60 system), 18.99 for 2005 epoch (N2005 system).
Hope this helps. ilkka
Hi Ilkka Korpela . Thank you for your reply. I am trying this in Nepal (44N) and on the raster dem data. What do you suggest in case like this?
Dear Rabi, I'm not familiar, which geoid model is the most valid in Nepal, if you have one develeped by national land survey, or if you need to rely on some global model that based on satellite gravimetry. But the principle is simple once you find a good-quality raster. I hope that you find it. Below the first entry with "Nepal Geoid model" search. Cheers, ilkka
Article Geoid Determination and Gravity Works in Nepal
Thank you IIKKa. I will look forward to the attached article. Have a good day!
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