Newbie here. I apologize if my question is if it has been dealt with already.
Because I had time, I thought I would place my RS3 at a known point and try different methods to determine the most accurate. My closest NTRIP caster is a CORS at a 22.5km baseline. So, I tried varied lengths of averaging time with a Fix and a Single solution. The location data looks good, but the height comparison has the most significant error. I’m not sure if it’s a problem with how I got the height from the datasheet or what. My understanding is to take the NAVD88 Ortho height and add it to the Geoid height.
Have a look at these images and let me know what you think.
To compare the elevations of two points, they need to be related to the same vertical datum or ellipsoid. If I understand correctly, the elevations of your points are ellipsoidal heights, so they can’t be compared with the orthometric heights in NAVD88.
Can you please share the points you collected in a CSV file and the link to this benchmark’s page? Thanks!
I’m not actually measuring points around the known location. I’m measuring the known location as a base with different techniques to see which one gets me the closest to the information on the datasheet. The X and Y look very accurate, but the Z height is not.
As far as I know, you’re doing the right thing. Ortho + geoid height = ellipsoid. In any case, if you were doing it wrong, your fix results wouldn’t be that close.
For your SINGLE results, it’s logical to have those inaccuracies. For your FIX ones, I’m kind of wondering if the base you’re using has a ~60cm difference between the APC and the actual coordinates it broadcasts.
What datum is the NTRIP caster sending corrections for? Maybe some version of ITRF and not NAD83? You are looking at NAD83 coordinates.
Yes, the NAD83 ellipsoid height will be 69.136-32.611 = 36.525 meters. You are getting (from your 10 minute sample) 35.745 meters. A difference of 0.78 meters. Not so close. What if your NTRIP caster is giving you a ITRF position? What’s the ITRF2020 or 2014 height for AH9140? It’s 35.770 meters. Reasonably close to your 35.745 meter value. NGS HTDP software was used to compute the ITRF value.
Do confirm what datum your NTRIP caster is working in.
You seem to be doing it right (Ellipsoide - Geoid). CORS is ITRF and ellipsoid height is used thus your rover is ellipsoid height too, so you just need to apply the Geoid which seems to be -32.611.
The monument you measure is quite old. From 2002.It could of due to earth crust movement
The monument is labeled stability code D, which is not good.
I am very grateful for all of your input. Thank you so much! This is a fantastic community of users. I have this all set aside in my notes for the next time I need to set up on a known point.
Now, to set up a Windows VM on my Mac so I can install and figure out the NGS HTDP software.
