Gps – Navigate Through Its Parts
So far, we all know GPS or Global Positioning System is one of the vital apps required while you are on move. This navigating science tells us everything about a particular location. While brushing over the past, we have come to know lots about its origin. The ancestors of GPS were ground-based navigators working on radio signals like Decca Navigator and LORAN. In 1960, the first satellite named Transit paved way for GPS signaling and US Navy then used it. Since 1973, this system has gone through various innovations making it applicable in every field.
To be acquainted with working of GPS, first we need to know the names of its various parts:
Satellite
Geo stationary orbit
Receiver
Signaling structure
Therefore, the most important part is Satellite. It transmits messages in the form of signals, which includes time of signal transmission and orbit specifications (main orbit-ephemeris and other orbits- almanac). There are 24 to 32 GPS satellites revolving the Earth. To calculate the precise position of GPS device, usually 3 satellites are enough to create three dimensional images. It should be noted that the speed of signal is equal to the speed of light. So when a minor clock error (errors that usually occur during calibrating the correct position) is multiplied with the speed of light then it may result to a major error in position determination. Therefore, 4 satellites provide a correct pseudo range for calculating the location. For those who are unaware of this term, pseudo range is the distance between a satellite and its receiver.
Geo stationary orbit is an orbit or path of GPS satellites present directly above the Equator of Earth. The advantage of rotating in Geo Stationary Orbits is that antennas of these GPS devices do not have to move around for tracking its satellites.
The GPS Receiver plays a major role in defining the position. It has four uses:
Handheld positioners
Differential GPS
Relative positioning GPS (DGPS)
Kinematics GPS
Before we go into the detailing of receiver types, we need to get familiar with Signal Structure parts. The GPS Signal Structure has five major parts:
C/A code on Carrier L1
P-code on carrier L1
P- code on carrier L2
Phase of carrier L1
Phase of carrier L2
Therefore, the first type of receiver monitors C/A code on carrier L1. They are outdoor units, which has an accuracy of 95% while calculating latitude and longitude of the position. It also shows precise altitude up to 180 meters. The received signals can be used to provide range and directions to waypoints, which is very much required by professional hikers. Differential GPS is the field receiver having a precision of 2 meters and are installed with memories for storing data thereby comparing it with field data for better precision. It works in both C/A mode and phase of L1 carrier.
The surveyors refining accuracy to a few orders of centimeter usually use DGPS. It works on dual frequency L1 and L2 thereby correct positioning takes place up to 30 km. Kinematics GPS gives true measurements used in the high-speed objects or vehicles. Hence, the above description of the parts surely is very much informative for GPS users.
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