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."

Comments

Black Mesa

[bonch]

But the effect in continental interiors -- on states not near the edge of those plates -- was a new one, the scientists said. Whether an upwelling in the gooey mantle that lies beneath the crust or a sag in the plates themselves, what exactly drives the growth remains a mystery.

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.

Re:Black Mesa

[bonch]

There actually is a Black Mesa, New Mexico, though I don't know if the in-game location has any relation (I imagine there are probably several Black Mesas in the deserts of America.

Re:Black Mesa

[PRMan]

Actually, I recently drove through New Mexico and was surprised by the green fields, grazing animals and tons of nice-looking farms/ranches along a long stretch of road. It was not what Looney Tunes said it would be (that was Arizona).

Re:Black Mesa

[mjwx]

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.

Well, if you were building a secret lab to run probably illegal experiments into inter-dimensional travel with the potential to bring vicious invaders to earth, which part of New Mexico would you pick.

There go my plans

[rbowen]

So much for driving to California next summer. It'll be farther away by then.

Re:There go my plans

[R3d M3rcury]

Perhaps I'm taking this too literally...

I'm not sure New Mexico can get any wider--it's borders are set along latitude and longitude lines. So it's more likely that Albuquerque will eventually end up in Arizona and Santa Fe will end up in Texas.

Re:There go my plans

[Anonymous Coward]

I'm not sure New Mexico can get any wider--it's borders are set along latitude and longitude lines.

It's borders are not defined by the latitude and longitude lines, but by the markers set by the surveying team which attempted to follow the latitudes and longitudes. In pretty much every country, certainly all regions of North America, boundaries that were intended to follow specific latitudes or longitudes don't change as our ability to more accurately define these imaginary lines on the globe. Typically the act in Canada or the U.S. that defines the national, state/province or county borders as following specific lat. or long. lines also includes the phrase "as defined by" and the specific survey mission that defined the border using the technology then available.

So every border that is popularly defined by a latitude or longitude is rarely accurate as the technology was often quite crude compared to what we can do today.
Therefore, yes New Mexico can and is getting wider and Albuquerque and Santa Fe are going to remain part of N.M. as long as some kind of hispanic revolution doesn't occur. ;-)

The Obesity Epidemic

[Anonymous Coward]

...is so bad in the United States now, even the GROUND is getting fatter.

Re:The Obesity Epidemic

[rts008]

Why do you hate America?
High Fructose Corn Syrup!!! Where's the Beef? Supersize me!
Wahoooo!

Not News

[sunderland56]

Yeah, yeah, we know - America is getting fatter.

Re:Not News

[MichaelSmith]

And then there is the expansion of the universe to consider. Whats's the red shift of Mexico City right now?

Re:Not News

[R3d M3rcury]

Yeah, but it's not that bad--1 inch every 40 years. Personally, I added about an inch in the past year.

Re:Not News

[L4t3r4lu5]

The leading political party is liberal, so I'd say it's more of a blue shift. This very handily brings us back to the Half Life comments at the top.

Apparently a side effect of resonance cascades is pre-destination and determinism.

Re:Slashdot has really gone downhill recently...

[jjjhs]

It's obviously Fox's liberal agenda to separate the poor and their filth from the rich as physically far as possible.

GPS Accuracy

[Proudrooster]

Fellow Slashdotters... this is a little off topic, but is there any way to get accuracy out of GPS? I can barely get plus/minus 12 feet of accuracy out of my GPS in the best conditions. How are they able to determine sub-inch accuracy? This sounds impossible, even with "25 extra-precise GPS receivers" as stated in the article. I just don't believe it is possible to measure to this level of accuracy with GPS. Someone please prove me wrong and school me how to build one with this accuracy for my autonomous lawn bot :)

Re:GPS Accuracy

[BitterOak]

They probably use techniques like differential GPS to increase their accuracy.

Re:GPS Accuracy

[tomhath]

A couple of years ago some coal miners were trapped underground in Pennsylvania. They brought in someone with super expensive GPS equipment to locate where to drill the rescue hole. As I recall he claimed he could fix the position within a few centimeters. Anyway, they drilled where he said and hit the chamber where the men were located, so he was either very good or very lucky. But don't expect your phone or other (non-special-government licensed) consumer device to be much better than a few meters.

Re:GPS Accuracy

[__aaltlg1547]

You use 2- frequency GPS receivers that are inherently less noisy and more accurate than the cheap ones everybody uses for coarse navigation. Then you average the position data over long times.

The longer you average, the lower the uncertainty in the position.

Re:GPS Accuracy

[weweedmaniii]

If they use military-grade GPS systems they can get sub-inch accuracy. All everyone else can get a lot less accurate. One of the reasons China is putting up their own satellite constellation for the own GPS-type system, so they can achieve the same accuracy our system has. I suspect they either can't crack the coding to use the more accurate system, or more likely they have cracked it and reverse engineered it.

Re:GPS Accuracy

[imidan]

Stationary GPS is a little bit different. The receiver is planted in a location whose coordinates can be very carefully determined via more traditional survey methods. Combine this with some other technologies, and you can get very precise and accurate results. For example, one of the factors that degrades the accuracy of GPS is atmospheric effects. With a network of carefully surveyed stationary GPS units, we can correct for atmospheric effects by seeing how 'off' the various units are compared to normal, and to each other. There are other sources of error, but the point is that GPS error can be greatly reduced when you already know where you are.

Now, in this case, the 'stationary' GPS units are actually moving at a very slow rate. With the error corrections described above, once all the other errors are accounted for, what remains is error due to actual movement of the GPS. I can't see the full text of the paper, but probably what they have is a statistical model that says the GPS units are moving by a certain amount each year, and a confidence level, and all of that.

So, to your last point: if you want to improve the GPS accuracy of your lawn bot, you need only to install a stationary GPS receiver on your house, survey its location very carefully, and attach a transmitter to turn it into a 'GPS base station' that your robot's GPS will use as a local reference to improve its GPS fix. (You can buy a GPS base station from someone like Trimble; they're often used for construction and the like.)

Re:GPS Accuracy

[dido]

Differential GPS gets accuracy to up to 10 cm, which is just above 4 inches I think. It seems that it is possible to obtain even sub-millimeter accuracy from GPS, although I gather the techniques used aren't real-time, and as such unsuitable for mobile robotics. :( They work well enough for surveying though.

Re:GPS Accuracy

[FrankSchwab]

Differential GPS, as BitterOak said, as well as some exotic techniques of receiving the GPS signal, as well as certain signal processing approaches - you're measuring distances over a year; there's a lot of processing gain if you simply take a million readings and average them!

There's a good chart here http://www.geoplane.com/gpsneeds.html showing the cost curve as accuracy goes up.

Re:GPS Accuracy

[oneblokeinoz]

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.

Re:GPS Accuracy

[NatasRevol]

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.

Re:GPS Accuracy

[Anonymous Coward]

http://www.spacedaily.com/news/gps-00d.html

I'm not sure why people keep repeating this. Its not true, the civilian GPS is the same accuracy as the military since the Clinton administration.

They keep repeating it because it is true. Military GPS uses different signals which still result in better accuracy, even with the removal of selective availability.

From the US government's GPS page (emphasis added):

Is Military GPS More Accurate Than Civilian GPS?

The accuracy of the GPS signal in space is actually the same for both the civilian GPS service (SPS) and the military GPS service (PPS). However, SPS broadcasts on only one frequency, while PPS uses two. This means military users can perform ionospheric correction, a technique that reduces radio degradation caused by the Earth's atmosphere. With less degradation, PPS provides better accuracy than the basic SPS.

Re:GPS Accuracy

[tibit]

You should have perhaps asked someone who knows a bit about it, since those are all problems with known solutions. A GPS receiver that you can buy for less than USD $1k won't give you anwyhere near the accuracy you can pull out of the signal in realtime without using any differential techniques at all. For about $15-$20k in gear (multifrequency receivers with phase processing and ionospheric correction, large antenna, etc) you can get a couple mm of error in real time. Add to that another "nearby" receiver for a differential setup and your relative error can drop to well under a millimeter. Be prepared to spend good money for that. A good car's worth.

Re:GPS Accuracy

[maroberts]

I was working for a company on differential GPS back in 1992 and we were obtaining precision of less than a centimetre for differential GPS even then, real time. Admittedly "real time" was only about 1 update every 5 seconds or so but that was good enough for surveying purposes. Also we were generating an atomic reference clock using GPS to correct the receiver oscillator. If the resulting time signal was good enough for radio astronomy at Jodrell Bank, I presume it was good enough for anyone.... We were using 68000 processors (later 68020) backed up by custom ASICs; Clock speeds and power have come a long way since then.

Re:GPS Accuracy

[ThePeices]

Hummer? Kia?

He said a "good" car.

This is news?

[QuasiEvil]

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.

Re:Nevada too?

[c0lo]

Stretch marks?

The correct term is "nanostrain marks".

Re:Unit conversions

[tibit]

Nanostrain is a unitless unit. It means 10^(-9) in/in -- inches per inch. It's a relative measure of deformation, it always needs to be a applied to a length to give length. Just to look at orders of magnitude: 10 nanostrains over 100 miles = 10^(-6) mile = 0.6 in.

Re:Unit conversions

[mrchaotica]

"Strain" is expressed as length divided by length (e.g. in/in). In other words, it's a dimensionless ratio. Here's how we calculate it for this situation:

The length (actually width) of New Mexico is about 343 miles, which is 21,732,480 inches:

L = 2.1*10^7 inch

In a year it stretches 1/40 of an inch (on average):

dL = 2.5*10^-2 inch

Therefore the strain, dL/L is:

dL/L = 2.5*10^-2 inch / 2.1*10^7 inch = 1.2*10^-9

Voila: the inches cancel and you get 1.2 dimensionless "nanostrains."

Bugs Bunney was a trickster....

[rts008]

You took a wrong turn in Albuquerque....