Hi If you believe the 3 ns / M applies in this case, tides will give you about 1 ns or so. If the geometry of the motion (vertical) and the orientation of the sat’s is not same / same, the impact will be a bit less.
On an L1 system without some sort of ionosphere “help” and working just off of broadcast data, you can / will / may see > 10 ns per day. Troposphere is the same sort of thing only a bit less per day. There are a whole raft of interesting relativity issues that get into GPS. Again the L1 stuff does not do much beyond the in-system corrections. The biggie is ionosphere …. Bob > On May 24, 2015, at 8:02 AM, Attila Kinali <[email protected]> wrote: > > On Sat, 16 May 2015 04:41:15 +0000 (UTC) > Bob Stewart <[email protected]> wrote: > >> I did some idle searching trying to see if there was a relationship between >> terrestrial tides and timing receivers. I couldn't find anything useful, but >> I did discover that the Jersey Village area, about 2 miles northeast of me, >> is sinking about 2 inches a year. So, my question is what effect do either >> of these, terrestrial tides or this local sinkage, have on timing accuracy? > > I guess you are looking for the relationship between earth movement > and GPS/GNSS time transfer? If so, solid earth tides (as they are > commonly called in the timing community) do not become an issue until > a lot of other factors are removed first. First you need a system > that reduces multipath to a minimum, then one that can measure the delay > induced by the ionosphere directly (ie an dual/tripple frequency GNSS > receiver). I am not sure whether tropospheric delay or solid earth tides > come next, my guess would be that both are in the same order of magnitude. > > The size of solid earth tides can be up to 30cm (i think i read somewhere > that someone measured 50cm, but not sure), mostly in vertical direction > (horizontal to vertical has about a factor 10 difference in amplitude), > where GNSS precision is quite low (compared to horizontal precision). > It has to be corrected in precise GNSS augmentation systems like IGS > (see [1, page 12]). > > I am not sure whether anyone accounts for continental drift in timing > applications. I would guess that at least people in VLBI have to. > Given that most GNSS high precision time transfer is used rather locally > (a couple of 100km) and that few people are running it for more than > a couple of months without recalibrating the system, i'd say that the > drift rates (which are between 2.5cm(Arctic) and 15cm(Chile) per year) > do not induce much error/jitter. > > Attila Kinali > > > [1] "A guide to using international GNSS service (IGS) products", > by Jan Kouba, Version 2.1, 2009 > https://igscb.jpl.nasa.gov/igscb/resource/pubs/UsingIGSProductsVer21.pdf > > -- > < _av500_> phd is easy > < _av500_> getting dsl is hard > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
