A Generalized Navigation Correction Method for Airborne Doppler Radar Data

Uncertainties in aircraft Inertial Navigation System and radar-pointing angles can have a large impact on the accuracy of the subsequent airborne dual-Doppler analyses. Testud et al. (1995, referred as THL method), has been routinely applied to data collected by the airborne tail Doppler radars over flat and non-moving terrain. The navigation correction method proposed in Georgis et al. (2000, referred as GRH method herein) extended the THL method over complex terrain and moving ocean surfaces by using a variational formulation but its capability over a moving surface has yet to be tested. Recognizing the limitations of the THL method, Bosart et al. (2002, referred as BLW method) proposed to derive ground speed, tilt and drift errors by statistically comparing aircraft in-situ wind with dual-Doppler wind at the flight level. When combined with the THL method, the BLW method can retrieve all navigation errors accurately; however, it can only be applied to flat surface when there is enough radar echoes at the flight level, and it is rather difficult to automate the whole process. This paper presents a generalized navigation correction method (GNCM) based on the GRH method which will serve as a single algorithm for airborne tail Doppler radar navigation correction for all possible surface conditions. The GNCM included all possible variables in the cost function and implemented a new closure assumption by taking advantage of an accurate aircraft ground speed derived from the GPS technology. The GNCM is tested extensively using synthetic airborne Doppler radar data with known navigation errors as well as published data sets from previous field campaigns. Both tests show the GNCM was able to correct the navigation errors associated with airborne tail Doppler radar data with adequate accuracy.