Getting to Know GPS Technology
GPS (Global Positioning System) is a system of satellite navigation and positioning are owned and managed by the United States. The system is designed to provide positioning and three-dimensional velocity as well as information about the time, continuously around the world without relying on time and weather, to many people simultaneously. At this time the GPS is already widely used all over the world in various fields of applications demanding information about position, velocity, acceleration and time accurately. GPS can provide positioning information with accuracy vary from a few millimeters (a zero) up to tens of meters.
Some GPS capabilities, among others, can provide information about the position, velocity, and time are fast, accurate, cheap, anywhere on the Earth, without depending on the weather. It should be noted that the GPS is the only navigation system or the system of positioning within this century that has a powerful ability like it. Precision of GPS tracking can be achieve several mm to precision his position, several cm/s for thoroughness his speed and several nanosecond for accuracy his time. Precision position obtained will depend on several factors including the method of determining the position, the satellite geometry, the level of accuracy of the data, and method of processing data.
Products that GPS Given
In general the products of GPS is the position, velocity, and time. In addition there are several other products such as acceleration, azimuth, parameter attitude, the TEC (Total Electron Content), WVC (Water Vapour Content), Polar motion parameters, as well as some products that need to be combined with external information from other systems, its products include high ortometrik, geoid undulation, and vertical deflection.
Determination Principle of Positioning with GPS
The determination principle of positioning with GPS that use the method of resection of measurement of distance, where the distance is done simultaneously to several satellites have been known to its own coordinate. On the measurement of GPS, each epoknya has four parameters must be specified: the 3 parameters the coordinates X, Y, Z or L, B, h and one parameter time error due is not sync the clock oscillator in a satellite with GPS receiver clocks. Because of the required minimum distance measurements to the four satellites.
the Type Tool of GPS Receiver
There are 3 types of GPS devices, with each providing the level of precision (position) that different. The first GPS device type is the type of navigation (Handheld, Handy GPS). Type nagivasi the price is quite cheap, but the accuracy of the position given the current can reach 3 to 6 meter. The second tool is a type of type geo second single frequency (type mapping), commonly used in survey and mapping which requires precision position about centimetres up to several decimeter. The last type is a type geo second dual frequency which can provide accuracy of position to millimeters, this type is used for the application of precise positioning as the construction of the NET control point, deformation survey, and geodynamics.
Signal and Bias on GPS
GPS emitting two signal i.e. L1 frequency (1575.42 MHz) and L2 (1227.60 MHz). The L1 signal dimodulasikan signal with two pseudo-random i.e. code P (Protected) and C/A code (coarse/aquisition). L2 signal carries only the P code. each satellite transmits a unique code so that the receiver (GPS receiver) can identify the signal from each satellite. On the features of the “Anti-Spoofing” enabled, code P would be encrypted and then known as P (Y) code or code Y. when the signal through the atmospheric layers, then the signals will be disturbed by the content of the atmosphere. The magnitude of the disturbance called biased. Bias signal that consists mainly of 2 kinds of bias the ionosphere and troposphere bias. This Bias must be taken into account (modelled or being estimated or differencing techniques to perform differential method with the baseline distance wasn’t too long) to get the final solution coordinates with precision. If the bias negligible then it can give you the error position up to orde m.
Error Source on GPS
On the GPS system there are several fault system components that will affect the accuracy of the position obtained. Those mistakes e.g. wrong orbit satellite, satellite clock errors, errors at the receiver, the antenna phase Center error and multipath. Other things also there are accompanying system errors such as imaging, and noise effects. This error can be eliminated by using differencing data.
Positioning Method with GPS
Positioning method by GPS is first split into two methods, namely, the absolute and differential methods. Each method can then be done by real time and or post-processing. If the specified object is a silent position then they are called Static. Otherwise, if the specified object is moving, then his position called kinematik. Further more detail again we will find the methods such as the SPP, DGPS, RTK, GPS Surveys, Rapid Static, pseudo kinematik, and stop and go, and there are still some other methods.
Precision Position Obtained from the GPS System
For civil applications, GPS position accuracy providing value in a enough wide spectrum, ranging from meters to millimeters. Prior to May 2000 (SA on) the absolute accuracy of GPS positioning method with data psedorange 30-100 metres. Then after SA off accuracy improved to 3-6 metres. While the accuracy of DGPS Techniques give accuracy 1-2 metres, and engineering giving RTK accuracy 1-5 centimeters. For a position with the accuracy of millimetres afforded by the technique of GPS survey equipment GPS dual frequency type of geo second and the strategies of certain data processing.
Applications of GPS Technology
GPS (Global Positioning System) satellite navigation system is the most popular and most widely applied in the world at the moment, both on land, sea, air, and space. In addition to military applications, GPS application areas are quite evident at this time include the mapping survey, geodynamics, geodetic, geological, geophysical, transportation and navigation, monitoring deformation, agriculture, forestry, and even sports and recreation.