DEVELOPMENT OF GPS SATELLITE VISIBILITY SIMULATION METHOD UNDER URBAN CANYON ENVIRONMENT

Abstract. When the UAV is flying in a lower area than the buildings in the urban environment, the GPS positioning accuracy of the aircraft reduced due to the blocked or reflected signals. Therefore, when the UAVs fly in this area, it should be able to provide a criterion that can give warning message to the UAV users such as stop the auto-flight mode or not rely too much on the position of the UAV represented on the monitor of GCS. In this study, the Elevation Mask Profile (EMP) generation algorithm proposed which calculates azimuth and elevation angle ranges blocked by obstacles at certain grid points by using DSM. It is a core algorithm for a GPS simulator developed that predict the blocked satellite signal by matching the EMP calculated for each grid point with the GPS satellites' azimuth and elevation angle information at the grid point. According to the comparison of EMP and observed data, most of the results had correlation with obstacles nearby. We found some signal blocking areas were not determined as EMP due to the skyscrapers located out of the target area where DSM was constructed. To overcome this limitation, larger spatial data than the DSM that used in this study must be applied. Furthermore, additional studies about optimal search radius definition in EMP calculation procedure to acquire more accurate and standardized EMP are necessary.