Application of IGS Products for Air Navigation

Single Point Positioning (SPP) method is widely used in air, marine, and land navigation to determine the user’s position in real time and post factum. A typical accuracy for this method of determining the user’s position in the static mode is approximately 10 meters. In air operations, the SPP method accuracy can be several times lower and that may cause problems with precise positioning of an aircraft. The authors of this article presented preliminary results of research concerning aircraft positioning in the kinematic mode based on GPS observations. For this purpose, an in-flight experiment, in which a Cessna 172 aircraft was used, was performed at the airport in Mielec, Poland. The aircraft was equipped with a dual-frequency Topcon TPS HiperPro receiver, which was recording satellite observations with 1-second interval. The aircraft position was determined using the least-squares method (LSM) in the RTKLIB (RTKPOST module) software. Two research tests were performed within the scope of the experiment, i.e. in test I the aircraft position was determined on the basis of raw GPS observations and the broadcast ephemeris data whereas in test II precision products of the IGS were used, such as: precise ephemeris SP3, DCB hardware delay, clock bias data of GPS satellites and receivers in the CLK format, data of the ionosphere maps based on IONEX format, and phase center calibration of GPS satellites and receivers in the ANTEX format. The use of the IGS precision products improved the accuracy of the X coordinate to 1 m, Y to 0.7 m and Z to 1.3 m. On the basis of tests I and II, an additional RMS-3D parameter was determined, whose mean value was 4 m.