GPS capability
Some GPS capabilities, among others, can provide information about the position, velocity, and time is fast, accurate, inexpensive, anywhere on earth without depending on the weather. It is worth noting that GPS is the only navigation system or positioning systems in some of this century that has such powerful capabilities. The accuracy of GPS can reach a few mm for the accuracy of its position, a few cm / s for speed and accuracy of several nanoseconds for time accuracy. Position accuracy obtained will depend on several factors: the positioning method, the satellite geometry, the level of data accuracy, and data processing methods.
Products supplied GPS
In general, products from the GPS are position, velocity, and time. In addition there are several other products such as acceleration, azimuth, attitude parameters, 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, products include high ortometrik , undulasi geoid and vertical deflection.
The principle of positioning with GPS
The principle of positioning with GPS is using the method of resection of the distance, where distance measurements carried out simultaneously to multiple satellites of known coordinates. At the GPS measurements, each epoknya has four parameters that must be determined: the three parameters of the coordinates X, Y, Z or L, B, h and one time due to parameter errors in the satellite ketidaksinkronan clock oscillator with a clock in the GPS receiver. Therefore, a minimum required distance measurements to four satellites.
Type of equipment (Receiver) GPS
There are three types of GPS devices, with each providing a level of accuracy (position) which is different. The first type is the type of GPS Navigation (Handheld, Handy GPS). Type nagivasi price is quite cheap, about 1-4 million dollars, but the accuracy of the current position given the new can reach 3 to 6 meters. The second type of tool is a single frequency geodetic type (type mapping), commonly used in survey and mapping that takes a position accuracy of about an inch up to several decimetre. Last type is the type of geodetic dual frequency which can provide position accuracy to achieve millimeter. This type is commonly used for precise positioning applications such as construction net of control points, deformation surveys, and geodinamika. Geodetic type receivers prices are quite expensive, reaching hundreds of millions of dollars for one unit.
Signal and Bias on GPS
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 (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 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 GPS
Method of determining 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, GPS Surveys, Rapid static, pseudo-kinematic, and stop and go, and there are still some other method.
The position accuracy obtained from the GPS System
For civilian applications, 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 GPS survey techniques with GPS equipment dual frequency geodetic type and specific data processing strategies.
Applications of GPS Technology
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
Know Your Benefits As well as the term in the GPS
Having a GPS without knowing their role? should avoid it in, because if we have a GPS we also need to know what the usefulness of GPS, here are some uses of GPS
Vehicle tracking
Navigation
Military
Monitoring earthquakes
Geographic Information Systems
For the purposes of Geographic Information Systems, GPS is often also involved in creating the map, such as measuring the distance of the border or as a reference measurement.
How does GPS work?
How GPS works, we can divide into five stages or GPS concept that works as follows:
1. Basic concept of GPS is triangulation from several satellites. Triangulation method is a method of determining the point of using the principles of the triangle
2. To make the process of triangulation, a GPS receiver to measure the distance on the basis of the time required by a radio signal to travel from the transmitter that is in our GPS satellite to the receiver.
3. To measure the length of travel time, GPS needs very accurate time which is achieved by doing some tricks or ways.
4. Along with distance, we also need to know exactly where to position the GPS satellites are located. The key is to find high-orbit satellites to monitor the GPS and the GPS satellites in the orbital.
5. Lastly, you must correct for any delay in the GPS radio signal after passing through the journey through the layers Atmospere
Behind it all, in fact the basic idea of calculating the position using GPS is that we use the position of the GPS satellites in Space made a point of reference for determining the position of a point on the earth. With a highly accurate measurement of the distance of at least three GPS satellites we can determine position anywhere on earth with the triangulation method.
GPS System
GPS satellites circle the earth 2x a day
These satellites transmit signals to earth
Signal is used to calculate the position
Distinguish the transmitted GPS time to calculate the position
This time is calculated as the distance from several GPS satellites to calculate positions on the earth & its surface, including the exosphere
Basic GPS Work
Must have at least three GPS satellites to calculate a 2D position and movement.
With four satellites, the GPS we can calculate the 3D position position (latitude, longitude & altitude).
With the position information, GPS can calculate other data such as: speed, direction, trajectory, distance, distance to destination, sunrise & sunset, etc.
