CONSTRUCTION OF NOMINAL IONOSPHERIC GRADIENT FOR GROUND-BASED AUGMENTATION SYSTEM IN INDONESIA REGION

• Main Author: Supriadi, Slamet
• Format: Dissertations
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/79851
• Institution: Institut Teknologi Bandung

Ground-Based Augmentation System (GBAS) is a GNSS augmentation system that meets International Civil Aviation Organization (ICAO) requirements to support precision approach and landing. GBAS is based on the local differential GNSS technique with reference stations located around the airport to provide necessary integrity and accuracy. The performance of the GBAS system can be affected by the gradient in the ionospheric delay between the aircraft and the reference stations. A nominal ionospheric gradient, which is bounded by a conservative error bound, is represented by a parameter ?vig. ?vig is commonly obtained from Continuous Operating Reference Station (CORS) data using spatial methods by single difference between stations (station-pair) and temporal method by single difference between epochs (time-step). The station-pair method is prone to doubling of receiver bias while the time-step method still contains temporal variations so that it is not suitable for CORS conditions in Indonesia. We propose a satellite-pair method and a time-step correction method. Both of these methods can eliminate the effect of receiver bias. Satelite-pair method propose 5.21 mm/km for Indonesia region. In addition, the ?vig value can be obtained by the time-step method using only one receiver. Based on the simulation, the ?vig value from the corrected time-step method is proven to be close to the results of other methods. The correlation value of the time-step method with all spatial methods is quite large (mixed-pair = 0.841, station-pair = 0.837, and satellite-pair = 0.816). These results are used to analyze changes in ?vig spatially and temporally in the Indonesian region. This study also includes the relationship between the nominal ionospheric gradient and space weather activity.