Transforming NAD 83 to present day GPS

ashton · 2021-09-19T15:29:00Z

I'm an aerospace education officer and involved in search and rescue with the Civil Air Patrol. I have one member who claims drones can achieve accuracy in the millimeters. Maybe the high-end setups with multiple-frequency receivers and real-time corrections against one or more reference stations could do a lot better than the typical hand-held hiking GNSS unit, if not millimeters, but certainly not the setup he's using. We agreed that we would observe some NGS monuments to establish what our equipment is capable of. Equipment includes drones (that I'm not very familiar with) Garmin eTrex (yellow, so old it doesn't have a number) Garmin eTrex 20 (personal equipment) Nikon D7100 with Solmeta GPS attachment various personal smart phones with cameras Motorola APX 4000 radios with build-in GPS that can display lat/long on the handheld radio. My question: I know that the NAD 83 NGS datasheet positions shouldn't be directly compared with GPS positions, and they can be transformed using NGS's HTDP software. One mark, OD0251, has the following horizontal position line: OD0251* NAD 83(2011) POSITION- 43 29 32.16709(N) 072 58 22.77824(W) ADJUSTED This is available directly as the "from" reference frame in HTDP. Assuming the GPS observations are made this year, what should the "to" reference frame be? The closest I could find was ITRF 2014. I realize the correction will only be on the order of a meter, which is on the same order of magnitude as the uncertainty of position of the best passive marks. But I want to be able to show the program output to anyone who is claiming millimeters. This, of course, is academic. One doesn't need accuracy to millimeters to find a crashed plane or a lost person.

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GNSS & Geodesy

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The ITRF

A .pdf file outlining what the ITRF "is" and where it comes from (and where it is going).

https://www.iau.org/static/science/scientific_bodies/divisions/a/2018/Altamimi.pdf

Posted : September 20, 2021 10:56 am

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Transforming NAD 83 to present day GPS

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