An Improved Algorithm for Receiver Implementation of ARAIM
Paul Massatt and Andrew Binder, The Aerospace Corporation
Advanced Receiver-based Autonomous Integrity Monitoring (ARAIM) requirements and algorithms have been developed within the aviation community to support primary means of aviation flight operations using multiple (two or more) global navigation satellite systems (GNSS). Concerns have been raised by different receiver developers regarding the amount of processing that could be required of the receiver. In preparation for such changes, the Aerospace Corporation has, under the support of the US Air Force, developed receiver implementation algorithms that improve efficiency. Projections are used to simplify calculations. Receiver processing efficiency is improved by separating the evaluation of quantities that are slowly changing in time from those that can rapidly change in time, and by significantly reducing the number of test metrics through reliance upon the independence of the test metrics from the state space solution. This is anticipated to reduce the number of tests per iteration from over one hundred to fewer than ten. The algorithms employ low rank updates to evaluate solution separation tests for various fault modes. The paper also addresses efficient methods for meeting fault exclusion requirements for horizontal ARAIM in order to meet continuity requirements. Results will be published showing the efficiency improvements achieved through the use of these algorithms. In summary, this paper describes methods for improving the efficiency of horizontal ARAIM and vertical ARAIM. The paper addresses satisfaction of both integrity and continuity requirements.