What is the function of the Global Positioning System GPS?

Answer 1

http://www.britannica.com/ebc/article-9365690?query=GPS&ct= Global Positioning System (GPS) Concise Encyclopedia Article Page Precise satellite-based navigation and location system originally developed for U.S. military use. GPS is a fleet of more than 24 communications satellites that transmit signals globally around the clock. With a GPS receiver, one can quickly and accurately determine the latitude, the longitude, and in most cases the altitude of a point on or above Earth's surface. A single GPS receiver can find its own position in seconds from GPS satellite signals to an accuracy of one metre; accuracy within one centimetre can be achieved with sophisticated military-specification receivers. This capability has reduced the cost of acquiring spatial data for making maps while increasing cartographic accuracy. Other applications include measuring the movement of polar ice sheets or even finding the best automobile route between given points. Review of handheld GPS' http://www.epinions.com/GPS_Devices/search_string_~GPS/adv_search_~1

Answer 2

It was not until the 20th century that ground-based radio navigation systems were introduced. Some are still in use today. GPS is a satellite radio navigation system, but the first systems were ground-based. They work in the same way as does GPS: users (receivers) calculate how far away they are from a transmitting tower whose location is known. When several towers are used, the location can be pinpointed. This method of navigation was a great improvement, yet it had its own difficulties. An example of such a system is LORAN. Each tower had a range of about 500 miles and had accuracy good to about 250 meters. LORAN was not a global system and could not be used over the ocean. Because ground based systems send signals over the surface of the earth, only two-dimenstional location can be determined. The altitude cannot be calculated so this system could not be applied to aviation. The accuracy of such systems could be affected by geography as well. The frequency of the signal affected accuracy; a higher frequency would allow for greater accuracy, but the user would need to remain within the line of sight. The first global navigation system was called OMEGA. It was a ground-based system but has been terminated as of 1997.

Satellite navigation systems can provide high frequency signals allowing for high accuracy, as well as global access because the satellites are so high up that remaining within the line of sight of the satellites is easy.

Answer 3

GPS is a precision navigation system developed for the US Military and maintained by the US Air Force Space Command in El Segundo, CA. The initial specifications were written in the early 1980s. The system consists of a constellation of at least 24 transmitting satellites, so that 12 will always be above the horizon anywhere in the world. Each satellite contains a precision atomic clock (periodically monitored and adjusted by the Air Force from the ground) and is assigned a long pseudorandom identification number, which it transmits along with a data block containing its clock time and various other status parameters. This system of satellites is available for both military and civilian use (however the military has priority and in a war can garble the civilian signal causing unpredictable random location errors in standard civilian GPS receivers).

When a GPS receiver somewhere is able to pick up and identify 3 or 4 GPS satellites signals, it can use a method called triangulation to compute its coordinates on earth in latitude/longitude and if it has 4 signals the altitude. If the receiver gets more than 4 signals it can reduce the error in the calculation and improve the accuracy of the coordinates. I am deliberately leaving out the technical details of how this is done, as it is beyond the scope of this question.

Such a GPS receiver is connected to a navigation computerof some kind, that translates the coordinates into something useful to the user (e.g. a moving map display showing his location and locations of nearby "points of interest", a targeting display showing the relative position of a site to be attacked).

Some businesses (e.g. trucking companies) program the navigation computers in the GPS unit in their vehicles to log routes, speeds, etc. to keep track of their drivers, that they aren't taking unauthorized side trips or driving unsafely. However this has nothing to do with GPS and is not part of GPS, its just another use of the data made available by that system.

Answer 4

is used for the scientist to look in globe

Answer 5

it's used to tell you where you are and how to get where you want to go