@ARTICLE\{IMM2015-06879, author = "J. Jakobsen and A. B. O. Jensen and A. A. Nielsen", title = "Simulation of {GNSS} reflected signals and estimation of position accuracy in {GNSS-}challenged environment", year = "2015", keywords = "Global navigation satellite system; navigation; non-line of sight; position accuracy; reflected signals; simulation", pages = "47-56", journal = "Journal of Geodetic Science", volume = "5", editor = "", number = "", publisher = "De Gruyter Open", note = "DOI: 10.1515/jogs-2015-0006. See also my lecture note: Least Squares Adjustment: Linear and Nonlinear Weighted Regression Analysis, {URL} http://www.imm.dtu.dk/pubdb/p.php?2804.", url = "http://www.degruyter.com/view/j/jogs.2015.5.issue-1/jogs-2015-0006/jogs-2015-0006.xml?format=INT", abstract = "The paper describes the development and testing of a simulation tool, called QualiSIM. The tool estimates {GNSS-}based position accuracy based on a simulation of the environment surrounding the {GNSS} antenna, with a special focus on city-scape environments with large amounts of signal reflections from non-line-of-sight satellites. The signal reflections are implemented using the extended geometric path length of the signal path caused by reflections from the surrounding buildings. Based on real {GPS} satellite positions, simulated Galileo satellite positions, models of atmospheric effect on the satellite signals, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the environment we are able to estimate the position accuracy given several prerequisites as described in the paper. The result is a modelling of the signal path from satellite to receiver, the satellite availability, the extended pseudoranges caused by signal reflection, and an estimate of the position accuracy based on a least squares adjustment of the extended pseudoranges. The paper describes the models and algorithms used and a verification test where the results of QualiSIM are compared with results from collection of real {GPS} data in an environment with much signal reflection." }