[time-nuts] tracking position & orientation

[Bob kb8tq]

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 <tvb at LeapSecond.com> 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:
>> eric at scace.org said:
>>>    I moved to Boulder CO a few months ago. The “curiosity� 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 -- time-nuts at lists.febo.com
>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.