Method for accuracy improvement of GPS measurement in the city

GPS (Global positioning System) is a 3-D positioning system using space satellites. Recently, the use of GPS in the city as the navigation system is rising continuously. However the measurement error is large when the receiver is used near the buildings such as in urban canyon. This reason is that the receiver is not able to measure a pseudo range accurately because of receiving reflected wave (multipath) from the obstacle. Then we suggested new methods for reducing the multipath error. They are methods which are discrimination of the presence of the multipath error using the signal strength, and calculating the multipath error using two kinds of measurements. We devised methods of positioning which does not require reference station in real time. In this paper, we show the effectiveness of our method with measurement results.