New Mexico Is Stretching, GPS Reveals
Velcroman1 writes "New Mexico's borders are gradually gaining girth, according to the Albuquerque Journal. It's not much, and it's not happening very fast — the state is getting about an inch wider every 40 years — but the state is unquestionably expanding, according to University of Colorado geophysicist Henry Berglund and his colleagues. Using a collection of 25 extra-precise GPS receivers planted across New Mexico and Colorado, Berglund determined that the cities of Albuquerque and Santa Fe are creeping away from each other. The rate of change seems ever so slow to the untrained ear, described as approximately 1.2 'nanostrains' per year."
Probably those experiments over at Black Mesa. By the way, the portrayal of New Mexico in Half-Life always amused me, with the cartoonish Looney Tunes cliffs and plateaus. With the exception of the northern area of the state, it's mostly just weeds as far as the eye can see, littered with the occasional beer can. We have good Mexican food, though.
So much for driving to California next summer. It'll be farther away by then.
Apache guy, Open Source enthusiast, runner
...is so bad in the United States now, even the GROUND is getting fatter.
Yeah, yeah, we know - America is getting fatter.
They probably use techniques like differential GPS to increase their accuracy.
If I can be modded down for being a troll, can I be modded up for being an orc, or a balrog?
Seriously? The entire Rio Grande Valley - which pretty much covers a north-south line right down the middle of the state - is a rift valley. The continent has been splitting and spreading here for millions of years. It's an interesting measurement, to be sure, and it's nice to have confirmation, but it shouldn't come as much of a surprise.
The key thing is that this level of accuracy is not achieved in realtime.
The receivers would be recording more than the information contained in the GPS messages, they would be recording phase and signal strength data for all the satellites in the visible constellation.
Sophisticated post processing software would combine this information across multiple receivers, along with published satellite ephemeris data, to produce an accurate position solution.
Realtime positions cannot be that accurate due to affects like ionospheric refraction etc.
I used to work with a mobile system that recorded the GPS data along with inertial information (at 200Hz) that in realtime gave a solution that was usually accurate to within 30cm, and got to better than 10cm when combined with static ground station data in the post-processing step.
There are systems used in agriculture that are very accurate (10cm-ish) that use differential-GPS in realtime. The trick is your mobile unit has to be in constant communication with the differential ground station. Works ok for tractors, not so well for an aircraft 200-300km away. For differential-GPS to work well both units need to see the same satellites.
They also use very large antennas (relative to commercial/handheld units).
The antenna's Henry is using are about 20" across and have some shielding to protect from signals reflected from the ground.
See:
http://facility.unavco.org/kb/questions/325/5%7B47%7D8%22+Stainless+Steel+All-thread+Mast+Overview
I know, because I work there.
There are two types of people in the world: Those who crave closure
You took a wrong turn in Albuquerque....
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti