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|Title:||Metode natancnega dolocanja polozaja s satelitskim sistemom GPS in njihova uporaba pri arheoloskih terenskih raziskavah / The Methods of high accuracy positioning using the satellite system GPS and their archeological field survey applications|
|Authors:||DIMC Franc; MUSIC Branko; VAN WIMERSMA GREIDANUS Herman; OSREDKAR Radko|
|Abstract:||The GPS positioning technology is well known and much used in many fields. However, due to its relative inaccuracy (100 m nominal accuracy of standard equipment) it is not used frequently in archaeological fieldwork, even though it has much to offer in these applications also. GPS equipment (receivers) is relatively cheap, easily portable, offers real time fixes, and make kinematical positioning possible, all of which is very attractive in such fieldwork. Commercial interest in the archeologically unexplored sites, before any development or building operations can commence, often requires extensive preliminary geophysical measurements and archaeological surveys. It is now well known that many of the positioning problems investigated in prospecting work will be solved by better basic accuracy in new satellite positioning technologies, based on a new satellite networks that are now under construction (Galileo, GLONASS, Beidou). As the new systems seem to be several years from becoming operational, the necessary experience in the geophysical fieldwork can be obtained by using existing satellite positioning systems, augmenting the GPS data by independent, complementary positioning systems. The vulnerability of the satellite navigation systems, due to intentioned jamming and the rate of errors due to the observation conditions, also leads to the implementation of such sensors. Our goal was to achieve a reliable 40 cm accuracy, deemed sufficient for archaeological fieldwork. We were concerned primarily with the horizontal accuracy of positioning, which is of major importance in archaeological fieldwork, leaving the more difficult problem of vertical positioning for a future project. One of the goals of our fieldwork was establishing a database by automatic logging of the geophysical survey data provided by positioning. This requires time triggering and/or event triggering of the logging process, and a synchronization of the process with fix acquisition. The idea of application of an inexpensive, single frequency GPS system is based on the need for flexibility and effectiveness in ¿extensive¿geophysical surveys. A tailored combination of GPS and inertial system data was thus analyzed and tested in order to improve the accuracy of each sub-system and the compound system. The necessary calibration results (accelerometer and magnetometer bias, noises) were obtained and evaluated to employ the Kalman filtering (KF) into positioning calculations for the purpose of archeological prospecting. For the purpose of position calculations from the micro electromechanical system (MEMS) accelerometer output an original experimental setup by mass on a spring is proposed. Also a comparison of double integration (DI) and KF on acceleration data was executed based on total variation. After an introductory Chapter 1, the subject matter of the dissertation is divided into chapters: In Chapter 2, basic parameters of global navigation satellite systems (GNSS) are presented, with the emphasis on the GPS. Basic characteristics of the GPS are analyzed and a description of GPS data analysis given, together with modern methods of processing for enhanced position accuracy. A tailored combination analysis of GPS and inertial system data is presented in the Chapter 3. In Chapter 4, an original experimental setup consisting of a mass on a spring is proposed for the purposes of position calculations from the MEMS accelerometer outputs. Also, a comparison of DI and KF on acceleration data was executed on the basis of total variation. In Chapter 5 the options of GPS receiver and inertial navigation system (INS) integration are reviewed. A loose coupled solution is adopted for the use in a system where a magnetometer as a only attitude sensor. Finally, the Chapter 6 brings the results of various static and kinematic field tests of the positioning equipment, performed on ten different sites.|
|JRC Directorate:||Space, Security and Migration|
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