  This letter addresses the 3D coverage path planning (CPP) problem for terrain
reconstruction of unknown obstacle rich environments. Due to sensing
limitations, the proposed method, called CT-CPP, performs layered scanning of
the 3D region to collect terrain data, where the traveling sequence is
optimized using the concept of a coverage tree (CT) with a TSP-inspired tree
traversal strategy. The CT-CPP method is validated on a high-fidelity
underwater simulator and the results are compared to an existing terrain
following CPP method. The results show that CT-CPP yields significant reduction
in trajectory length, energy consumption, and reconstruction error.
