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Bolivian Salt Flats Aid Spacecraft Calibration
PCOL writes "Salar de Uyuni is a vast plain of white salt in the mountains of Bolivia, with a total elevation range of less than 80 centimeters - the flattest place on earth. Beginning in 2002, geophysicist Adrian Borsa led a survey that resulted in precise GPS measurements of the salt flat. The flats will be used as a giant calibration device for satellite-based radar and laser altimeters on the CryoSat recovery mission so the spacecraft can more precisely monitor changes in the elevation and thickness of polar ice sheets and floating sea ice. 'Satellites can calibrate their altimeters by bouncing signals off the ocean surface .. because of atmospheric interference, tides and waves, there are uncertainties. Borsa says the salar, now so accurately mapped and with dry, clear skies, is about five times better than the ocean as a reference point.'"
And I have probably had a bit too much to drink, so forgive the deeply philosophical question.
When they mean that it's the "flattest place on Earth", do they mean that it conforms exactly to the curvature of the earth (thus not REALLY flat but earth shaped sort of flat), or is it FLAT flat, as in a chord across the curvature of the earth at that point...
Sorry, just trying to work out the meaning of "flat" on a round planet... blame the rum.
Seven puppies were harmed during the making of this post.
Yeah, just don't let Boyd Coddington anywhere near those salt flats. Look what he did to the Bonneville Salt Flats this year when I was out taking photos.
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... doesn't that mean that if anyone started mining the salt there, all navigational devices are hosed, because there is no normal anymore to calibrate them?
The dried Bonneville Salt Flats (open to the public) and its attached military only area called the Dougway Proving Grounds are the flattest place on earth. They have been used by the military for the past 40+ years to calibrate space and weapons systems. Pretty much every land speed record has been made at the Bonneville Salt Flats, including breaking the sound barrier. The variation of altitude is so minimal that it is within the accuracy of the measurement equipment used to calibrate altitude variations, but it has been certified to be less than 1 foot of elevation for every 10 miles.
And every year it gets 'reset'... The springtime runoff from the surrounding mountains will cover the entire salt flats with a perfect 1/2" of water. It is SO COOOL to go out there when there is a *PERFECT* sheet of water covering the salt, it looks like the worlds largest piece of glass. You can actually *SEE* the curvature of the earth. I have a picture of a much younger me 'walking on water' because it is so smooth you cannot tell that the water is only 1/2" (1.5cm) deep.
Working out on the salt flats, doing surveys, the survey crew would drive out 1 mile and hold up a survey marker. At five miles out we could not see them any more, we asked them to raise it up over their heads and we saw the marker rise up over the horizon like it was the sun coming up.
Because it is the worlds largest and flattest spot on earth, my father, an engineer in flight optics systems, has built optical calibration targets used by the military to calibrate autopilot systems, weapons guidance systems, terrain following radar systems, satellite optics systems and all that jazz for the military... which is why I grew up in Utah, am intimately familiar with the flats, and know without a doubt that my dad has worked on black projects that I hope someday he'll be able to tell me about (including flights into and out of the Janet terminal).
Good security is based upon reality and common sense. Common sense is a function of having common knowledge.
I had a remote sensing professor at the University of Arizona that frequently took road trips with his students out to remote areas in Nevada to calibrate imaging sensors. For this, the absolute flatness isn't as important as the high reflectance of the dry lake beds they use. Here is more info.
Oh yeah!?! Well, the Bonneville Salt Flats are 125452549094400.2 Square Millimeters!!! ahem...
If this is accurate (and it does appear to be), Bolivia is much, much bigger. You could lose Bonneville salt flats in Bolivia. I would also further speculate that both locations are equally flat as the salt will form a flat, equally distributed surface whenever it rains. I know from survey after survey that the Bonneville Salt Flats are within the margin of error for the measuring equipment to even detect variations in uniform surface 'flatness' where the margin of error is within 1' (30.48cm) altitude for 10 miles (16.09km) linear distance.
All my life I heard how they were the largest, flattest spot on the earth - so I assumed it was true because people from around the world went there to race.
Good security is based upon reality and common sense. Common sense is a function of having common knowledge.
I've been there. It's already being mined for salt. Not only do they leave holes but they leave the salt in conical piles to dry out (the water table is quite close and actually pools on the surface in some locations).
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show