Joegeodesist, post: 450069, member: 6744 wrote: Eppur si muove!
The NGS CORS long-term plots have not updated since 2012, they should refresh by early 2018 when NGS finishes reprocessing of all CORS data using IGS14 reference frame. This should also provide improved coordinates, velocities, and discontinuities (earthquakes and equipment changes). That reprocessing is reasonably automated (given the millions of files involved) until you get out west, where sites careen around like drunken sailors.
The NGS CORS short-term plots are generated from a special "net" version of OPUS which holds only the IGS frame as fixed. Normal OPUS obeys the National Spatial Reference Frame contention that all official coordinates are golden, though it does add HTDP to move things back and forth through time using the (from 2012-era) computed and modeled velocities. Many CORS were new back then and the velocities are relatively immature.
OPUS-S is now trained to solve from 5 nearby CORS and ignore the worst two solutions, so if only one CORS walks off from the official published position, OPUS should ignore it. For belt-and-suspenders, it also has an occasionally-updated blacklist of CORS to ignore, which includes these errant sites, mostly in California and Alaska.
The next reference frame won't be as beholden to these local motions, by design it takes off of ITRF with a simple clockwork-style Euler pole correction to remove all of the steady continental drift, and provides results at survey epoch (vs NSRS epoch 2010.0) Users can move points through time using an intra-frame velocity model (ala HTDP) to try to account for all of the localized variations, and the huge regional deformation out west where the Pacific plate drags California northward. This frame should be more honest and easier for to maintain, though it means that some local users will have to get used to their "control" drifting slightly over time. Eppur si muove indeed!
Thanks Joe!
We are all (or most all of us) looking forward to the upcoming changes (both igs14 AND NATRF2022).
It might be a bit of a bumpy ride for some though (still time to check those shock absorbers).
😎
Loyal
Joegeodesist, post: 450069, member: 6744 wrote: OPUS-S is now trained to solve from 5 nearby CORS and ignore the worst two solutions, so if only one CORS walks off from the official published position, OPUS should ignore it.
When was this algorithm implemented? Might I get different results if I re-submitted a session from early this year?