The joys of smoothing

Navigation post-processing or smoothing is the process of optimizing all navigation estimates based on the entire measurement set. For underwater vehicles this gives much smoother and more accurate estimates than what is obtained in real-time. The enhanced quality of the smoothed estimates is shown in this paper by examples from autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs) and tow-fish, using HUGIN or HAIN navigation systems. Also shown are the many valuable uses of smoothed data, like fault detection, fault identification, system calibration, and parameter identification. The only drawback of smoothed data is the fact that they are not available online, but at a lag. The profit of smoothing with reference to the time smoothed over (lag) is investigated for the test cases.