Thomas King Stephan Kopf Thomas Haenselmann Christian Lubberger Wolfgang Effelsberg COMPASS: A probabilistic indoor positioning system based on 802.11 and digital compasses. 34-40 2006 WINTECH http://doi.acm.org/10.1145/1160987.1160995 conf/mobicom/2006wintech db/conf/mobicom/wintech2006.html#KingKHLE06