Know About GPS Technology #Part 2

 Continuation from #Part 1

Signal and Bias on GPS

of GPS signal is emitting two frequencies L1 (1575.42 MHz) and L2 (1227.60 MHz). L1 signal is modulated with two pseudo-random signal is the code P (Protected) code or C / A (coarse / Acquisition). L2 signal carries only the code P. Each satellite transmits a unique code so that the receiver (of GPS receiver) can identify the signal from each satellite. At the time of the feature "Anti-Spoofing" is enabled, then the P code is encrypted and subsequently known as the code P (Y) or code Y.

When the signal through the layers of the atmosphere, then the signal will be disturbed by the content of the atmosphere. The amount of interference is called bias. Bias signal that is mainly composed of 2 kinds of bias ionosphere and troposphere bias. This bias must be considered (modeled or estimated or perform differencing techniques for differential method with a baseline distance is not too long) to get the coordinates of the final solution with good accuracy. If the bias is ignored then it can give up the position errors of the order of meters.

Error Source on of GPS

In GPS systems there are some errors system components that will affect the position accuracy of the results obtained. Mistakes are for example the satellite orbit errors, satellite clock errors, receiver clock errors, antenna phase center errors, and multipath. Other things are also there to accompany the effects of system errors such as imaging, and noise. This error can be eliminated one of them by using the techniques of data differencing.



Method of determining the position of the of GPS

Method of determining of GPS position with the first two, the absolute method, and the differential method. Each method can then be done by real time or post-processing. If the specified object stationary position then the method is called static. Conversely, if the specified object position moves, then the method is called kinematic. Further more we will find more detailed methods such as tuition, DGPS, RTK, of GPS Surveys, Rapid static, pseudo-kinematic, and stop and go, and there are still some other method.

The position accuracy obtained from of GPS System

For civilian applications, of GPS provides position accuracy value in a fairly broad spectrum, ranging from meters to millimeters. Prior to May 2000 (SA on) the accuracy of GPS positioning with an absolute method of data psedorange reach 30-100 meters. Then after SA off accuracy improved to 3-6 meters. Meanwhile DGPS technique provides 1-2 meter accuracy, and precision engineering provide 1-5 centimeter RTK. For positions with millimeter accuracy provided by of GPS survey techniques with of GPS equipment dual frequency geodetic type and specific data processing strategies.

Applications of GPS Technology

of GPS (Global Positioning System) satellite navigation system is the most popular and most widely applied in the world today, both on land, sea, air and space. Besides military applications, GPS applications fields are quite rampant at this time include the mapping survey, geodinamika, geodesy, geology, geophysics, transportation and navigation, deformation monitoring, agriculture, forestry, and even sports and recreation. In Indonesia alone, the use of GPS has been started since a few years ago and continues to grow until now, both in volume and type of application

Continue to #Part 3