GPS SURVEY
The Global Positioning System (GPS) is a satellite-based positioning system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the exact position of them. GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. With the distance measurements from a few more satellites, the receiver can determine its position with centimeter accuracy.
Thoughts
Have you guys read the article about Survey Earth in a Day 2.0 on the Ning Blog called Cultivating Community?
http://cultivate.ning.com/ning-blog/community-spotlight-survey-the-...
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TOTAL STATION SURVEY
A total station is an optical instrument used in modern surveying. It is a combination of an electronic theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as data collector. A total station allows the surveyor to store all information he needs to establish a setting out and can store all information taken from site as existing features, original ground levels, road edges, etc.
Also the remote measurements are facilitated by the total station where a direct access is not available. For example the height of street light poles, ground clearance of overhead power lines, etc.
Ron Thanks for correction.
Basically correct, except for the use of the word "triangulation". It is "trilateration" that should be used. Triangulation is the determination of a location by the measurement of angles. Trilateration is the determination of a location by measurement of lengths of lines. GPS measures line lengths from satellites to receiver.