Five Things You Probably Didn’t Know GPS Could Do
by Alexandra Witze/Knowable Magazine/Smithsonian.com
You might think you’re an expert at navigating through city traffic, smartphone at your side. You might even hike with a GPS device to find your way through the backcountry. But you’d probably still be surprised at all the things that GPS — the global positioning system that underlies all of modern navigation — can do.
GPS consists of a constellation of satellites that send signals to Earth’s surface. A basic GPS receiver, like the one in your smartphone, determines where you are — to within about 1 to 10 meters — by measuring the arrival time of signals from four or more satellites. With fancier (and more expensive) GPS receivers, scientists can pinpoint their locations down to centimeters or even millimeters. Using that fine-grained information, along with new ways to analyze the signals, researchers are discovering that GPS can tell them far more about the planet than they originally thought it could.
Over the last decade, faster and more accurate GPS devices have allowed scientists to illuminate how the ground moves during big earthquakes. GPS has led to better warning systems for natural disasters such as flash floods and volcanic eruptions.
Carol graduated from Riverside White Cross School of Nursing in Columbus, Ohio and received her diploma as a registered nurse. She attended Bowling Green State University where she received a Bachelor of Arts Degree in History and Literature. She attended the University of Toledo, College of Nursing, and received a Master’s of Nursing Science Degree as an Educator.
She has traveled extensively, is a photographer, and writes on medical issues. Carol has three children RJ, Katherine, and Stephen – one daughter-in-law; Katie – two granddaughters; Isabella Marianna and Zoe Olivia – and one grandson, Alexander Paul. She also shares her life with her husband Gordon Duff, many cats, and two rescues.
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I agree Dave that this is a “gimme” article. However I have hands-on experience with the centimeter accurate GPS systems used by seismic survey crews to find oil. Also, as a former sailor I am also quite familiar with a sextant and the spherical triginometry required to calculate position. One second in celestial accuracy, which is almost impossible to obtain, is still a lot of ocean. GPS can be jammed and spoofed. Look up the term Selective Availability in reference to GPS to learn more.
Wiki/Earth_tides
GPS had accurate horizontal control for surveying, but had vertical anomaly. The next generation showed an equatorial vertical movement of 18″ in conjunction with average 3 ft ocean tides. Earth’s thin cooled crust floats on molten, plastic mantel and the Moon is the motive force for tectonic plate movements. There is NO UNIVERSAL REFERENCE PLANE for sea level changes.
Ultra precise GPS has been around (even in the civilian world) for some time now. The accuracy of standard GPS (without intentional degredation) is about 100 to 300 feet. It takes enhancements to get the centimeter accuracy that seismic requires. Standard enhancement uses radio stations that have been carefully surveyed. These stations then send the corrections to a GPS receiver to improve accuracy. Even more enhancements are used by survey crews. Like the Trimble system for instance. But they are very expensive, and are used chiefly by survey crews and the military. For more information contact companies like Trimble.
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