The real-time kinematic (RTK) is one of precise positioning methods using Global Positioning System (GPS) data. In the long baseline GPS RTK, the ionospheric and tropospheric delays are critical factors for the positioning accuracy. In this paper we present RTK algorithms for long baselines more than 100 km with estimating tropospheric zenith wet delays. The state vectors as unknown parameters are estimated by the extended kalman filter (EKF). To verify the performance of the GPS RTK positioning, many baselines of more than 100 km were selected, and data processing was carried out. We show the experimental results of GPS RTK for various by using GPS data from the Korea Astronomy and Space Science Institute (KASI), National Geographic Information Institute (NGII) and one International Global Navigation Satellite System (GNSS) Service (IGS) reference station located in Japan. As a result, we present that long baseline GPS RTK can provide the accurate positioning for users less than few centimeters.

Keywords: GPS, RTK, long baseline, tropospheric delays