Assessment of Atmospheric Delay Correction Models for the Japanese MSAS

This paper aims to evaluate the potential error involved in the application of the recommended algorithms and the consequent effects on the positioning errors, under typical atmospheric conditions for MSAS (Multi- Functional Transport Satellite Satellite-based Augmentation System). The results and analysis presented in this paper will serve as benchmark for further development of MSAS. In order to assess the accuracy of Wide Area Augmentation System (WAAS) atmospheric models and their applicability to the Japanese MSAS, different analyses were carried out. Japan has different climates according to the region because of the North-South length. Airport locations and the weather in Japan were first studied. Tropospheric delay corrections obtained from the SBAS model were compared with Saastamoinen and Hopfield models that use temperature, air and vapor pressures as their input. The normal values for such meteorological parameters were taken from the Rika Nempyo (Chronological Scientific Tables) published by the National Astronomical Observatory of Japan. The data from flight tests conducted in the summer and winter as well as data for a week collected at 2 control stations were processed and analyzed. The stations located near Sendai and Naha airports were selected. Relative comparisons for positioning using different atmospheric correction models were made and preliminary results were obtained. The differences in height (vertical component of position) brought using different tropospheric correction models were less than 50 cm from our results. The SBAS troposheric model would be applicable to Japanese MSAS. The use of different ionospheric correction models (Klobuchar and dual frequency) provided the difference of 2.5 m in vertical component. Development of a correcion model for the ionosphere would be necessary. Some areas occasionally have poor satellite geometry. A ranging capability of MTSAT would be important in some areas over Japan.