Hi Indeed, I do a better job of detecting the impact of humidity ( = rainy season ) on my deck then I do detecting anything else on a fairly short baseline. I *do* get correct distances and angles between the antennas (as verified with a tape measure).
One thing you can do (with some effort) is to collect a lot of data. There is nothing magic about a 24 hour run. A two week run is also do-able. Lots of data will *not* take care of all problems. It will get the portion related to SNR down to some very small numbers. For continental drift sort of things, find a solid chunk of rock. If it’s connected to something very deep, that’s best. Tie the antenna to it, possibly with a fairly short mast. Best to have a good view of the sky so a short mast may not be practical. In the various papers on the subject you see antennas on a 2’ mast mounted on tops of hills if it’s a “quick” setup. ===== If you are going to all the trouble of setting up three or more L1 / L2 systems with good antennas on them *and* monitoring that for months / years ….. I’d suggest that watching the PPS out of each of the receivers might be interesting as well …. :) The uBlox units mentioned earlier do have a PPS out that is pretty good. They have a cousin, the F9T that is slightly more timing oriented. The F9P board is a much better deal / easier to get. (though uBlox *is* very quick at shipping the F9T’s direct from Europe). Bob > On Nov 22, 2019, at 5:00 AM, Tom Van Baak <[email protected]> wrote: > > Eric, > > Good idea to experiment with an antenna on each end of the house. You'll get > all sorts of data and your eyes will be eager to read house movement into the > plots. The problem is you won't know for sure if the results are real or not; > there are many factors, especially for a house made of wood. See plots for my > home/lab. [1] > > So a suggestion is to place at least one of the antenna on a waterproof > turntable and continuously rotate it, off center, very slowly, maybe one turn > a week, or month. Then look at your data and see how well you can detect that > *known* movement. > > By comparing actual GPS data with your calculated turntable antenna location > you can establish the position detection sensitivity of your setup. Which is > to say, if you can't detect a *known* antenna movement of a few inches around > a month there's little chance that you're going to confidently detect an > *unknown* seasonal or tectonic ground motion of a few mm a year. > > Alternatively, use a waterproof linear XY stage and each midnight shift the > antenna 1 to 12 inches north and 1 to 31 mm east based on the month and day > number. At the end of the year you will have created the coolest GPS plot > ever seen. It's kind of a slow motion version of "geowriting". [2] > > /tvb > > [1] http://leapsecond.com/pages/quake/ > > [2] http://leapsecond.com/pages/geowrite/ > > > On 11/21/2019 11:36 PM, Hal Murray wrote: >> [email protected] said: >>> I moved to Boulder CO a few months ago. The “curiosityâ€� is to >>> determine >>> the position of two antennas at either end of my house and monitor it over >>> time, with the idea that one could see plate movement in 3 dimensions plus >>> rotation around the axes. >> How much does Boulder move? I'd guess not much so measuring motion will be >> tough. You could try to get a lower limit on the speed. >> >> Looks like that part of the country is not interesting to the USGS: >> https://earthquake.usgs.gov/monitoring/gps >> >> Ballpark numbers. >> With a good setup, GPS gives location to about 1 mm. >> I live a few miles from the San Andreas fault system. It is shifting about >> as fast as your fingernails grow, roughly an inch per year. >> >> Measuring rotation will be tough if your 2 stations are only 100 ft apart. >> Do >> you have a friend 1, 10, or 100 miles away? >> >> PS: Make sure that your antenna mounts are sturdy. You don't want them >> drifting as the house ages or you bump into them. >> >> ---------- >> >> There is a major USGS campus on the Boulder side of Denver. You might wander >> down there and ask around to see if you can find anybody familiar with either >> GPS or earthquakes. Or try their web pages. There is probably a public >> information contact. >> >> ---------- >> >> >From a USGS talk tonight on Sea Level Rise. >> California is rising about 2 mm per year. Sea level is rising about 3 mm >> per year. Net is 1. >> East coast is sinking about 3 mm per year. >> (Major risk is surge and waves from hurricanes.) >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
