Simulation of GNSS Satellite Availability in Urban Environments Using Google Earth

Taro Suzuki and Nobuaki Kubo

Abstract:	In this paper, a novel method to simulate global navigation satellite system (GNSS) satellite availability in urban environments is proposed. Owing to the increased need for positioning in urban and mountain areas, an analysis of GNSS availability and accuracy is required under conditions in which satellite visibility is low due to obstacles that block GNSS signals. The positioning accuracy depends on the number of satellites and the dilution of precision (DOP) satellite geometry. However, the DOP and actual received satellite signals depend on the surrounding environment of the GNSS antenna. The prediction of positioning accuracy and availability, which can account for the surrounding environment, such as buildings, is needed in many outdoor applications. We therefore propose a method to directly estimate GNSS satellite visibility using Google Earth based on so-called virtual fish-eye sky image generation and without using laser scanning data or three-dimensional (3D) city models prepared in advance. Google Earth provides accurate 3D city models of many downtown areas throughout the world, even in locations where tall buildings block GNSS signals. First, a virtual image of the zenith point in the specified location is captured with Google Earth. Then, a virtual fish-eye image is generated from the nonlinear transformation of the captured image. The obstacle area in the virtual fish-eye image is extracted using a simple image binarization technique. The GNSS satellite position, which is calculated based on satellite orbit information, is projected onto the binarized fish-eye image. Satellite visibility is automatically determined by monitoring the overlapping pixels of the binarized fish-eye image. To confirm the effectiveness of the proposed technique, a positioning test was conducted in a real-world ‘urban canyon’ environment. The results demonstrate that the proposed method can accurately simulate visible satellites and that the exclusion of signals from invisible satellites, which are blocked by buildings, can improve GNSS positioning availability and accuracy in urban environments.
Published in:	Proceedings of the ION 2015 Pacific PNT Meeting April 20 - 23, 2015 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	1069 - 1079
Cite this article:	Suzuki, Taro, Kubo, Nobuaki, "Simulation of GNSS Satellite Availability in Urban Environments Using Google Earth," Proceedings of the ION 2015 Pacific PNT Meeting, Honolulu, Hawaii, April 2015, pp. 1069-1079.
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