Introduction to the Global Positioning System by Dr. Stephen C. Brown K-State Research and Extension Brown County And Mandy Kern Hiawatha High Agriculture Educator
WHAT IS GPS?• Satellite based radio positioning system• Developed and maintained by the U.S. Department of Defense• Made up of three segments: Space Control User or Ground receivers• Used for obtaining accurate locations anywhere on earth
Math Connection Step 1 •Suppose we measure our distance from a satellite and find it to be 11,000 miles. •Knowing that were 11,000 miles from a particular satellite narrows down all the possible locations we could be in the whole universe to the surface of a sphere that is centered on this satellite and has a radius of 11,000 miles.
Math Connection Step 2 •Next, say we measure our distance to a second satellite and find out that its 12,000 miles away. • That tells us that were not only on the first sphere but were also on a sphere thats 12,000 miles from the second satellite. Or in other words, were somewhere on the circle where these two spheres intersect.
Math Connection Step 3•If we then make ameasurement from a thirdsatellite and find that were13,000 miles from that one,that narrows our position downeven further to the two pointswhere the 13,000 mile spherecuts through the intersection ofthe first two spheres. •To decide which one is our true location we could make a fourth•So by ranging from three measurement. But usually one ofsatellites we can narrow our the two points is a ridiculousposition to just two points in answer (either too far from Earth orspace. moving at an impossible velocity) and can be rejected without a measurement.
PRACTICAL APPLICATIONS•Navigation •Sailing, hiking and aviation •Collecting and locating way-points•Locating Features • Stocking locations or stream surveys • Endangered or sensitive species locations • Locating trails or physical structures•GIS •Collecting GPS data along with attribute data • Mapping and database update•Surveying •Locating Control Points quickly
LOW END UNITS•Capabilities •20 ft accuracy •1-12 channel receiver •Collect only way point data•Cost •$80 - $600•Limitations •Poor reception under tree canopy •No file collection•Applications •Navigation for hiking or sailing
MID-RANGE UNITS•Capabilities • Sub-meter accuracy with DGPS • 6-12 channel receiver • Collects static, mobile and attribute data•Cost • $2,500 - $15,000•Limitations •Not accurate for surveying•Applications • Navigation • Mapping •GIS Update
HIGH END UNITS•Capabilities • cm accuracy with DGPS • 12 channel receiver • Collects static points•Cost • $15,000 - $100,000•Applications • Surveying
Garmin GPS Receivers Inexpensive and downloadable Available locally for less than $150 Most GPS receivers similar in operation
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