Sun Time-Sequence-Based Underwater Autonomous Positioning to Eliminate Positioning Ambiguity

Autonomous positioning is critical for autonomous underwater vehicles (AUV). The sun is a natural navigational clue that can be used by marine animals, and also an effective complementary navigation means for AUV. The current sun-based positioning methods use single-sun measurement of a separate time. However, the single-sun-based positioning strategy has the weakness of the positioning ambiguity in the present of low solar altitude. The false positioning solution of the ambiguity significantly affects the geolocation performance. Concerned with the challenge, an autonomous positioning method based on sun time-sequence measurements is proposed in this paper. A series of sun measurements in a time sequence are adopted to define the distance metric in kNN regression simultaneously, instead of separately. The time span and sun measurement frequency, as two critical parameters of the proposed method influencing the positioning performance, are analyzed quantitatively. This method fully utilizes the sun measurement, thereby eliminating the sun-based positioning ambiguity and improving positioning accuracy. Finally, substantial comparative simulations are carried out to evaluate the proposed method.