Some weeks ago I asked for a way to get heights in the german elevation system „NHN“ (Normalhöhenull), using the German Combined Quasi Geoid 2016 (GCG2016).
For small areas (500 x 500 m) i use the web app from the „Bundesamt für Kartographie und Geodäsie“ (the german geo agency) to get the offset i use for the whole Area. So i get an accuracy of +/- 3 cm (checked with well known points).
WebApp: Onlineberechnung von Quasigeoidhöhen mit dem GCG2016
So you did ground-truthing after the conversion and were getting within 3cm? Seems unlikely.
First I was wary too.
But i tryied it and it works.
For the correct east/north ellipsoid heigth i use the offical german RTK Service (SAPOS), the web service provides the geoid distance. So why should’t it work?
It depends on whether or not you are really measuring the ground. Ellipsoid and geoid are fine for theoretical elevation and if given the correct conversions and datum age should work against each other, but I personally have never seen those match true ground grade per a benchmark and a level. There is allot of confusion on this in these forums and when the term “accuracy” comes up I want to make sure we are on the same page. I’m still trying to learn how you guys are using theoretical information for a real world application. Who is the end-user of your data?
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