By Tom Logsdon
Duringthe PersianGulfWaragroupofAmericansoldiersscoopedup anew recruitatRijaid Airport, thendrovehim, withblackenedheadlights, at once throughout miles oftractless desertsand.Squintingtoward the horizon, hecould see virtually not anything while without warning the driving force mashed at the brakes, gave him a short salute, and urged him to step out into the darkness. As his bootssankintothesand, hewasstunned torealizethathewasonlyafew ft clear of the flap of his tent. ahead of starting off, the driving force had keyed the tent'scoordinates right into a Navstar receiver, so itcould advisor him again back. not anyone is aware precisely what number Navstar receivers ended up serving coalition forces alongside the Persian Gulf simply because moms and fathers-and sweethearts, too-located a couple of stray devices at the cabinets of marinesupply houses/plunked down their cash, and convey mailed them to their household within the Persian Gulf. a number of creative squaddies known as stateside providers lengthy distance, then used their charge cards to reserve receivers, a lot of which arrived in Saudi Arabiaa dayortwolateraboardcommercialjetliners. Bythe timetheground battle eventually all started, 4,000 to 7,000 Navstar receivers have been clutched within the arms of thankful American squaddies. They have been used to steer fuel-starved airplanes for linkups with aerial tankers, to tug in air moves opposed to enemy emplacements, to lead mess vans towards hungry troops, and to vector specific Forcesunits intheir muffled dune buggies deep behindenemylines. Afew enterprising army engineers discovered easy methods to keep on with meandering goat trails in order that they might find underground springs the place the goats wa tered themselves. They then used their handheld Navstar receivers to checklist the right coordinates of every spring, therefore insuring clean water provides for onrushing troops.
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Extra resources for The Navstar Global Positioning System
Although Omega achieves broad area coverage with only eight transmitters, its 2cr navigation error is quite large: 2 to 4 nautical miles. The transmitters operate in the 10 to 13 kilohertz range, with carrier waves that are approximately 16 miles long. When it is operated in the differential navigation mode, Omega's accuracy improves to 1,000 to 2,000 feet. In the differential navigation mode, two or more radionavigation transmitters exchange information with one another, so many of the positioning errors common to the two solutions can be eliminated.
The control segment The fully operational space segment will consist of 21 Block II satellites plus 3 active on-orbit spares arranged in six 55-degree orbit planes 10,898 nautical miles above the earth. Each Navstar satellite transmits a precisely timed binary pulse train together with a set of ephemeris constants defining its current orbit. The user segment consists of tens of thousands of Navstar receivers located on the ground, in the air, and aboard ships, together with a few aboard orbiting satellites.
The signal travel time multiplied by the speed of light (186,000 miles per second) equals the slant range from the satellite to the user. By measuring the instantaneous Doppler shift associated with those same four satellites, the receiver can also determine its three mutually orthogonal velocity components. All of the carrier waves streaming down from the satellites are right-hand circular polarized. This is accomplished by using 12 spiral-wound helical antennas arranged in a tight pattern. Four of them are located in the center quad.
The Navstar Global Positioning System by Tom Logsdon