Assessment of pseudolite layout under urban environments using a simulation system for seamless positioning

Abstract

Since the launch of the first Global Positioning System satellite, the demand for higher accuracy and wider applicability has been continuously increasing. In particular, personal navigation stresses requirements on “seamless” or continuous positioning with higher reliability are needed in urban areas. Unfortunately, urban canyons causing shadowing and multipath represent an adverse condition for Global Navigation Satellite System (GNSS) signal reception, thus leading to poor satellite visibility and low positioning accuracy. In order to overcome such problems, pseudolites can be set up to provide additional ranging signals and aid the carrier phase ambiguity resolution which is crucial for utilizing the full accuracy and wide range capability of GNSS. Pseudolites, which are ground-based instruments that transmit GPS-like signals, can improve the satellite-receiver layout and be used as additional range observations to improve the performance of a GPS-based deformation monitoring system. However, due to economic and environment constraints, the number of pseudolites that can be installed will be limited. More importantly, in order to reduce the areas affected by multi-path of pseudolite signals, locations and antenna pattern of pseudolites have to be carefully examined. This paper shows the development of a simulation system for evaluating the appropriateness and economics of installing pseudolites using precise orbital information of the satellite and a three-dimensional digital map.