Wi-Fi Assisted GPS Positioning with Fixed Geodetic Height

Since signals are blocked by tall buildings,there are always less than four GPS satellites inview in urban canyons,thus position information using standard point positioning may not always beavailable.Since the development of Internet,more and more Wi-Fi hotspots are being installed in cit-ies.In this context,this paper proposes a method called Wi-Fi assisted GPS positioning using onlythree satellites and fixed geodetic height.The proposed method includes two steps:firstly,the initiallatitude and longitude are obtained by Wi-Fi positioning using a weighted-centroid algorithm;then fi-nal coordinates are worked out by combing three GPS observations and the fixed geodetic height.Anexperiment was carried out in an opening area and results showed that,positioning precision,as com-pared with that of Wi-Fi positioning,is improved significantly with GPS positioning using the pro-posed method.