| Born of the best minds from a concept so simple | | | | The GPS tracking system's navigation message |
| is an exceptionalcomplex system, the GPS | | | | consists of time-taggeddata bits that mark the |
| tracking system. It is made up of | | | | time of transmission of each subframe at thetime |
| threecomponentsL satellites that orbit the earth, | | | | they are being transmitted by the space vehicle. |
| control and monitoringstations and the GPS | | | | A data bitframe consists of 1500 bits divided into |
| receivers. It is a radionavigation systemproviding | | | | five 300-bit subframes and adata frame is being |
| reliable positioning, navigating, and timing services | | | | transmitted at an interval of 30 seconds. |
| notjust for the military but also to civilian users as | | | | Thereare three six-second subframes containing |
| well in any partof the world. The GPS tracking | | | | orbital and clock data. |
| system has drastically changed theworld of | | | | Precise clock corrections are sent in subframe |
| navigation through land, sea and air, in all weather, | | | | one and orbital datasets or ephemeris data |
| 24/7. | | | | parameters for the transmitting space vehicleare |
| The Global Positioning System (GPS) is | | | | sent in subframes two and three. Various pages |
| a U.S. space-basedradionavigation system that | | | | of the system dataare being transmitted in |
| provides reliable positioning, navigation,and timing | | | | subframes four and five. So the GPS |
| services to civilian users on a continuous | | | | trackingsystem has an entire set of twenty-five |
| worldwide basis | | | | frames or 125 subframescreating the complete |
| -- freely available to all. For anyone with a GPS | | | | navigation message sent over a 12.5-minuteperiod. |
| receiver, the systemwill provide location and time. | | | | The GPS Tracking System Equipment on the |
| GPS provides accurate location andtime | | | | Ground |
| information for an unlimited number of people in all | | | | Ground stations are used so that each satellite |
| weather, dayand night, anywhere in the world. | | | | orbit are accuratelytracked. The GPS tracking |
| In the 1960s the U.S. Navy and Air Force worked | | | | system has ground stations which iscomprised of |
| together on a numberof systems that would be | | | | a receiver and antenna, as well as communication |
| able to provide a variety of navigationapplications. | | | | tools totransmit the data to the data center. |
| In 1973 the Department of Defense aimed to | | | | When the GPS satellites supplyspecially coded |
| direct theservices in unifying their systems. The | | | | signals, the omni-directional antenna at each |
| concept of the trackingsystem would be atomic | | | | sitepicks up the signals and that is processed in a |
| clocks onboard satellites was testedsuccessfully | | | | receiver. Thereceiver then separates the signals in |
| by an earlier Navy program called TIMATION. The | | | | various channels for aparticular satellite and |
| Air | | | | frequency at a particular time. Once thesignals are |
| Force would operate the new system called the | | | | isolated, the receiver now decodes them and |
| Navstar Global | | | | splits theminto individual frequencies to calculate |
| Positioning System. From then on, it has since | | | | position, velocity, directionand time anywhere on |
| been known as simply | | | | Earth. |
| GPS or Global Positioning System. | | | | At least four GPS satellite signals consisting of |
| The GPS tracking System Satellites | | | | space segments areused in computing positions in |
| Today's GPS Operational Constellation is funded | | | | three-dimensional locations - latitude,longitude and |
| and controlled by the | | | | altitude - and the time offset in the receiver clock. |
| U.S. Department of Defense and being operated | | | | All GPS tracking system satellites have |
| by the U.S. Military. | | | | synchronized operations sothat the signals are |
| It is comprised of three major components: a | | | | transmitted at the speed of light to theequipment |
| "constellation" ofsatellites in Earth orbit, ground | | | | on the ground. Each GPS satellite broadcasts |
| stations that controlled the systemand receivers | | | | dataindicating its location and current time. |
| hand carried by the users. It was so designed so | | | | Since the GPS tracking system sites are |
| thatthese receivers could be made small and | | | | constructed throughout theworld and are being |
| inexpensive and would notrequire atomic clocks. | | | | monitored by different institutions worldwide,there |
| The GPS tracking system is an aerospace | | | | are many different data center locations. The role |
| technology comprising of atleast 24 operational | | | | of the datacenter is to both monitor and control |
| satellites at all times. Each satellite is on acircular | | | | the GPS tracking systemstations. The data center |
| orbit 20,000 kilometers above the Earth on a | | | | uses an automated computer system inretrieving |
| 12-hour period. | | | | and analyzing data from the receivers. Once |
| In order to make sure that these satellites are | | | | processed, thedata, including the original raw data, |
| detected from anywhereon the surface of the | | | | are sent to scientists aroundthe glob for use in |
| Earth, the satellites are divided into sixgroups | | | | various applications. |
| having four space vehicles each. The six orbital | | | | From laboriously built landmarks by our ancestors |
| planescompletely surround the Earth, equally | | | | to shooting thestars to chronometers to satellites, |
| spaced 60 degrees apart and atan angle of about | | | | our technology has evolved fasterthan we could |
| 50 degrees with respect to the equatorial plane. | | | | ever imagine. The GPS tracking system is the |
| Each group is assigned a different path to follow. | | | | mostrecent and significant advancement in |
| The orbit altitudeis such, that the GPS satellites | | | | navigation and positioningtechnology. This new |
| recapitulate the same ground trackand | | | | constellation of artificial stars serves thisimportant |
| configuration at approximately over any point | | | | need for both the military and civilian users and is |
| each in 24 hours. | | | | nowfast becoming important in everyday life. |