Deeply integrated GPS for indoor navigation

This article discusses the results of a feasibility study designed to provide precise (cm-level) carrier phase GPS measurements indoors. There are existing approaches to provide low-accuracy (m-level) pseudorange GPS measurements, but they often require external aiding or they cannot provide the precision measurements needed for many applications. The approach used in this paper uses longer signal integration times along with advanced processing techniques to extract a complete set of measurements (carrier phase, pseudorange, and navigation data) from GPS under weak signal conditions without external aiding and provides a factor of 50 improvement over the tracking threshold of a traditional receiver and operates while in motion.