中文摘要：

在城市峡谷地区，由于高楼大厦的遮挡，GPS可视卫星数量往往不足4颗，无法正常定位；另一方面，随着互联网的发展，城市中的Wi-Fi热点越来越多，而且现在的数码产品（如智能手机）除了具备GPS定位功能外，还可以利用Wi—Fi信号无线上网。在此背景下，研究了利用城市泛在的Wi-Fi信号辅助GPS定位的方法。首先利用Wi—Fi信号定位获得初始的经纬度，考虑到Wi—Fi信号在高程方向的分辨率比较差，因此将观测区域的平均大地高作为先验的高程，从而获得概略的三维位置信息；然后利用高程可获得模式下的三颗GPS卫星观测值来进一步定位。实验结果表明，在加入了GPS卫星观测值后，定位精度与Wi-Fi定位初始结果相比有了明显提高。

英文摘要：

Since signals are blocked by tall buildings, there are always less than four GPS satellites in view in urban canyons, thus position information using standard point positioning may not always be available. 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 only three satellites and fixed geodetic height. The proposed method includes two steps： firstly, the initial latitude and longitude are obtained by Wi-Fi positioning using a weighted-centroid algorithm; then final coordinates are worked out by combing three GPS observations and the fixed geodetic height. An experiment was carried out in an opening area and results showed that, positioning precision, as compared with that of Wi-Fi positioning, is improved significantly with GPS positioning using the proposed method.