Performance is analyzed for an airborne tightly coupled inertial navigation system (INS)/GPS/electro‐optical imaging (EO) system that simultaneously estimates platform states, sensor biases, and unknown ground object coordinates using a single Kalman filter. Analysis is done by (1) comparing the performance of the INS/GPS/EO system with that of conventional tightly coupled INS/GPS navigation systems, (2) changing INS and GPS performance to determine the dependency on individual sensor performance, and (3) investigating the benefits of tracking a known ground object (control point). Simulation results show that (1) poor INS/GPS yaw angle accuracy is significantly improved by tracking an unknown ground object with the INS/GPS/EO system; (2) GPS performance has effects on platform position, velocity, and orientation accuracy, while INS performance has effects mainly on platform orientation accuracy; and (3) tracking a control point results in better navigation accuracy than tracking an unknown ground object, suggesting the possibility of using control points as an alternative to GPS.
Estimating the uncertainty or predicted accuracy of gridded products that are generated from historical bathymetric survey data is of high interest to the maritime navigation community. Surface interpolation methods used for gridding survey data in practice are well established. This paper investigates error estimation methods for gridded bathymetry in terms of their practical utility. Of particular interest are: 1) assessing the quality of a prior uncertainty of random error in survey data; 2) the significance of autocorrelated random errors; 3) the relationship between survey point density and propagated or product uncertainty; 4) the computational feasibility of Monte Carlo (MC) methods over large regions; and 5) the value of cross-validation to estimate error in the absence of controlled truth. K-fold cross-validation is used as the basis for performance evaluation of our approach to propagate a priori random errors via MC perturbation with spline-in-tension surface interpolation. Experiments are conducted with test areas in the Norwegian archipelago of Svalbard.
A new navigation system has been developed in which an imaging sensor is used as an aid to an airborne integrated INS (Inertial Navigation System) and GPS (Global Positioning System) system. We name it the tightly coupled INS/GPS/EO (Electro Optical System) system. In the current configuration, the EO measures single ground object image position through a camera on board an aircraft. As represented by the term "tightly coupled", the INS, GPS and EO are integrated using the single Kalman filter which estimates aircraft states, sensor biases and ground object coordinates simultaneously. As the consequence, aircraft yaw angle determination (an weak point common in INS/GPS systems) is greatly improved. Furthermore, the INS/GPS/EO system can also focus on known stationary ground objects (control points) resulting in improved navigation accuracy.
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