| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 97 === In these decades, satellite positioning is becoming a very important technique applied in our daily life. The basic principal of this technique is to determine a receiver’s location using range observations between satellites and the receiver. Therefore, the intervisibility between satellites and receivers is one of the most critical factors to the positioning quality. Typically, satellite positioning with a low obstruction will be more accurate and is thus preferred. The positioning quality can be pre-analyzed by identifying all visible satellites to a specific receiver. However, the topographic consideration in conventional planning software is usually neglected or simplified as a mask angle. Consequently, the results predicted by conventional software will not be realistic since detailed topographic data is not involved.
Fostered by the rapid development of spatial information technique, three-dimensional topographic information (e.g. Digital Terrain Model and Digital Surface Model) of a higher quality is becoming accessible to the public. This study aims to develop a satellite visibility and quality assessment technique utilizing high resolution 3-D topographic information. An adaptive sampling and analysis technique is proposed to increase the computational efficiency while processing topographic data of various grid resolutions. Additionally, a unified least squares approach is introduced to model the uncertainties of satellite orbits. Simulation tests and a GPS field work have been conducted to demonstrate the performance and capability of this approach. The results reveal a significant improvement on the reliability for the quality estimation of a satellite surveying. Consequently, the proposed approach will benefit the applications in which a pre-analysis of the positioning quality is of a major concern in a satellite surveying (e.g. a GPS filed planning or network design).
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