Design of a TRN Tracking Loop: a Study on GPS Multipath Mitigation Strategies

Abstract

Terrain Referenced Navigation (TRN) is based on the comparison of terrain altitude measurements with a reference map. Similar to code acquisition and tracking in Global Positioning System (GPS), the TRN system needs to find and track a particular sequence of measurements in a larger dataset. In our earlier work, these correspondences have been exploited to design a GPS inspired algorithm for TRN. The tracking loop is implemented as an early-late correlator, based on the DLL functional principle. Differences between GPS and terrain data in terms of signal properties are often based on the analysis of an ‘ideal’ GPS signal. In reality a GPS signal suffers from disturbances such as multipath and interference. This paper focuses on the identification and evaluation of potential GPS multipath mitigation strategies to be used to partly mitigate the issues caused by the non-ideal terrain signal. Results for the TRN implementations are described in a comparative manner. The content of this paper was presented during the European Navigation Conference 2011 in London.