All locating one unknown node requires at least four reference nodes in a three-dimensional space. If three reference nodes are used, then at least two places can satisfy the result of positioning in a wireless sensor network. Hence, on the basis of the boundary of sea level, the reference nodes are on the sea level below, whereas the unknown nodes are above. Here, we determine the solution of positioning both unknown and reference nodes with different spatial locations to find three reference nodes that are noncollinear and are the nearest to one unknown node. The experiment proves the accuracy of positioning with three reference nodes, which are furnished by the boundary of sea level. We conclude that the method of positioning that only uses three reference nodes can exactly realize the position and simultaneously increase the speed of positioning.

Aiming at the unsatisfactory performance of the particle swarm optimization algorithm in the optimization process of complex problems and being easy to fall into premature convergence, a power law function to improve the weight value of the particle swarm algorithm is proposed in the paper. It is compared with the linearly decreasing weight particle swarm algorithm, and the test is performed on four typical single-peak and multi-peak functions. The test results show that the particle swarm optimization algorithm in this paper has a better optimization effect.