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Darbe yra analizuojama GPS veikimo principai nuo palydovų iki pat naudotojui pasiekiamų signalų. Nagrinėjant šiuos principus visur atsižvelgiama į galimas paklaidas ir tiriama kokiu būdu jos yra taisomos, siekiant sistemą padaryti kuo tikslesnę. Atlikus sistemos veikimo analizę daromas bandymas, siekiant nustatyti realiai gautų GPS duomenų paklaidą, matuojant taško poziciją. Taip pat tiriama skirtingų gamintojų GPS imtuvų tikslumo priklausomybė nuo imtuvo procesoriaus kanalų skaičiaus. Paaiškėja, jog rinkoje parduodami GPS imtuvai dirba labai panašiu tikslumu. Toliau darbe atliekama naudojamų GPS duomenų tikslinimo algoritmų analizė ir pasiūlomas judėjimo rastriniu žemėlapiu algoritmas pozicijos nustatymo paklaidų mažinimui bei judėjimo prognozavimui nutrūkus ryšiui su palydovais. / This paper is a study of GPS operating principles from satellites to user-accessible signals. The examination is done by taking into account all the possible errors and how they are corrected in order to make the system more accurate. After system operation analysis tests of GPS data accuracy are made. The position of a point is measured using several GPS receivers. Those receivers are made by different manufacturers, so we can observe the dependency of accuracy according to manufacturer and different number of processor channels. It appeared that receivers have very similar errors. The work is continued by data accuracy improvement algorithms analysis. Finally an algorithm is suggested to improve positioning data precision moving on map and predict the event of a failure to communicate with satellites.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Since June of 1993, an experimental GPS receiver system has been orbiting the earth aboard a small, low-altitude, polar-orbiting satellite called RADCAL. The purpose of the experiment was to prove the concept of using GPS for satellite navigation. If successful, the system would also provide a backup to the satellite's primary navigation beacon. The goal: provide position and velocity data to an accuracy of three to five meters, and provide attitude data to within a degree. The configuration of the RADCAL GPS experiment precluded realtime feedback loops for navigation; the data was stored and downloaded after a designated collection period. On the ground, a lengthy process was used to yield the position and attitude data days after the collection event. The GPS receivers and ground equipment were configured in several modes; they ultimately yielded a position accuracy of five meters, and attitude of two degrees. This was the original goal, and the experiment was considered successful. However, one of the receivers failed in November 1993, and the other failed in January 1995. The GPS receivers were commercially available and not spaceflight proven; they were suspected of being vulnerable to single-event upsets and latchups. This turned out to be the cause of the failure of both receivers. The interface between the GPS receivers and RADCAL's other subsystems proved to be the area which could not tolerate corrupt data. The single-event latchups problems would ultimately lead to the failure of the receivers. These difficulties, as well as other lesser obstacles, provide a host of lessons learned for future satellite navigation systems.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Vehicle tracking system based on GPS has been paid more and more attention. The system consists of GIS (Geological Information System), master station, movable station and communication network. Movable stations installed on automobiles transmit their position and status messages to the master station. All vehicles' tracks are drawn on the electrical map displayed by the master station's computer screen in real time. Vehicles' alarming signals can also be transmitted to the master station simultaneously. This paper presents a whole designing scheme of the vehicle tracking system, then it makes a thorough introduction to the system's performance and working procedure. The key technologies employed by the system and the relations between them are also discussed in details in the paper.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / Future U.S. Navy at-sea and littoral battle group training range instrumentation requires a new, secure, high data rate link This link must be capable of providing the ranges with the capacity to increase the number of players, increase the amount of threat simulation, and allow an improved Global Positioning System (GPS) based position tracking system to be implemented This paper describes a Dual Function Transponder (DFT) capable of operating on any R-CUBED (Relay, Reporter, Responder) based range as well as any TACTS/ACMI range without modification of either range type. In addition, the DFT provides a new increased data rate capability for use by planned future ranges, enabling a dramatic increase in the number of participants as well as significantly increasing the quantity of data that can be communicated by each player. Miniaturization and programmability are the keys to this development and many of the methods used are described.