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GEODEETTINEN LAITOS |
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06.04.2001 kirjasto@fgi.fi |
SUOMEN GEODEETTISEN LAITOKSEN TIEDONANTOJA |
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| THE QUALITY OF REAL-TIME KINEMATIC (RTK) GPS POSITIONING by M. Bilker and H. Kaartinen Abstract Real-time Kinematic (RTK) GPS is more and more taking over traditional surveying tools, but about the quality of RTK measurements is not much published. This study investigated the quality of RTK addressing the questions: What is the accuracy of RTK GPS measurements, what influences these measurements and how can they be controlled? To find answers to these questions a literature study was performed and tests were made in rural areas with five different types of RTK equipment. The accuracy values specified by the manufactures are under good conditions: 10 mm + 1-2 ppm for plane coordinates and 15-20 mm + 2 ppm in height. The test results showed that these values were also met under less favourable circumstances. The user should be aware of many factors that influence the measurements. Factors inherent in the GPS-system are: the number of satellites, the satellite configuration, the atmosphere activity, and the baseline length. Factors coming with the choice of RTK equipment are: the software, the type of data-link, and the antenna types. Factors in the measurement environment are: the topography, obstacles, horizon coverage, multipath, and electromagnetic disturbances. The accurateness of the user is a factor as well as the measurement procedure which includes the number of measured epochs, the base station choice, repetition of measurements, one or more base stations, and most important the chosen coordinate system. The RTK equipment predicts the measurement accuracy well, but full control over the measurements is only obtained by independent repetition of the measurements and by regularly visiting points with known coordinates. |
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06.04.2001 kirjasto@fgi.fi |
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| Geodeettinen laitos Geodeetinrinne 2, PL 15 02431 MASALA |
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