Wykorzystanie analiz przestrzennych w wyznaczaniu położenia anten GPS stacji referencyjnej w Dziwnowie

Obecnie do wyboru odpowiedniej lokalizacji różnych sensorów można stosować przestrzenne analizy widoczności z wykorzystaniem Numerycznego Modelu Pokrycia Terenu. Standardowo wynikiem takiej lokalizacji jest klasyfikacja NMPT na obszary niewidoczne i widoczne. Znalezienie optymalnej lokalizacji wymaga przeprowadzenia wielu prób, które w zasadzie w sposób przybliżony, a nawet przypadkowy, wyznaczają hipotetycznie pozycję optymalną. W pracy zastosowano metodę, która jest rozwinięciem analizy widoczności, polegającej na wskazaniu obszaru lokalizacji spełniającego ustalone kryteria widoczności na obszarze opracowania. Wynikiem takiej analizy jest wyznaczenie dedykowanego obszaru lokalizacji anten, dzięki czemu można precyzyjniej określić ich docelowe położenie. Badania przeprowadzono dla stacji referencyjnej DGPS w Dziwnowie.

Spatial configuration of DGPS permanent reference station elements has an effect on a performance of the entire system. The arrangement of station elements, such as a broadcast antenna and reference masts, requires an allowance and a further linking together with a number of technical, operational and terrain factors. Some technical and operational factors as a rule are determined by the equipment manufacturer; however, terrain factors are conditioned by terrain character of the future reference station site. The terrain character is a composition of its surface shape and all geographical features situated within the reference station surroundings. These factors often can cause certain difficulties during recommended elements' arrangement of the planned reference station. This elaboration presents applications of visibility analysis in planning spatial location of the reference stations GPS antennas. Visibility, or viewshed, analysis is usually available in various computer programs of Geographic Information System environment. It can be performed from any point situated in the three-dimensional space of an elaboration range. In the case of such elements as permanent GPS antennas, application of visibility analyses solves the problem of their location with the allowance of the surroundings and geographical features, which can cause limitation of visibility of satellites and occurrence of multipath. Basically, by performing this kind of analyses, the three-dimensional position of GPS antennas can be determined, which meets such requirements as recommended horizon visibility. In this paper, the extended method based on viewshed analysis is presented. By using this method, the model of obturation factor can be created, which presents a continuous spatial distribution of its values within a possible area of the antennas placement. This feature allows for more precise area determination of the possible GPS antennas location. Additionally, by applying further analysis based on a raster arithmetic, the antenna height over ground can be assessed, which is also useful during making decision about future configuration of the reference station. The study was conducted in DGPS reference station in Dziwnów mainly used for marine navigation. The analysis results show the present state of the GPS antennas location and a possibility of its correction for a better performance of the whole reference station.