Algorithm 1: 3D passive underwater target tracking algorithm for the time-varying non-Gaussian environment by distributed underwater buoys

1. Optimal topology determination 1 Use every two out of three measurements from the buoys to form the observable measurements sets as $\left(1,2\right)$, $\left(1,3\right)$ and $\left(2,3\right)$; 2 Calculate the accuracy index ${\mathrm{T}}_{acc}$ of every topology of the distributed buoys by Equation (14); 3 Calculate the robust index ${\mathrm{T}}_{ob}$ of every topology of the distributed buoys by Equation (18); 4 Use the results from step 1 and 2 to calculate the overall index ${\mathrm{T}}_{all}$ by Equation (19); 5 With the preset index $\alpha$, determine the optimal topology of the distributed underwater buoys of tracking time $k$ by Equation (20). 2. Tracking the underwater uncooperative target by APF under the time-varying non-Gaussian environment 1 Based on the determined sets of measurements at tracking time $k$, initialize the first step particles and the relative weights; 2 Particles are time-updated by Equation (37); 3 Online noise estimation by Equation (39); 4 New weights are calculated by Equation (45); 5 Resampling procedure are checked and performed by Equation (47) and resampling method introduced by ref. [31]; 6 Estimate the current process noise by Equation (48); 7 Time propagation to run the whole algorithm at tracking time $k+1$.