On the Suitability of Ionospheric Gradient Estimation Techniques for IRNSS Based GBAS Applications

Abstract

Time-Step method and Station-Pair method are prominent techniques for estimation of spatial gradients. Since GBAS is meant to serve a limited area of about 50km of an airport for aircraft Precision Approach and landing, these two methods were considered for gradient estimation within the GBAS service area. Much of the work on these techniques has been reported for GPS-based GBAS applications. In this paper, the suitability of these methods to IRNSS-based GBAS applications is investigated. It is observed that since IRNSS satellites are either GEO or GSO, the time interval (At), of Time-Step method should be significantly high (30min for GSO), to obtain gradient data for GBAS’ service area. With the Station-Pair method, a dense network of stations, each separated by not more than 1–2 kms is required.