Automated artifact-free seafloor surface reconstruction with two-step ODETLAP

• Published in: SIGSPATIAL Special 2012-11, Vol.4 (3), p.8-13
• Main Authors: Lau, Tsz-Yam, Franklin, W. Randolph
• Format: Article
• Language: English
• ISSN: 1946-7729; 1946-7729
• DOI: 10.1145/2429177.2429179

We present an updated artifact-free seafloor surface reconstruction scheme which preserves more terrain features than our previous attempt using overdetermined Laplacian Partial Differential Equation (ODETLAP) and automates the adjustment of smoothing parameter. The high resolution version of such a surface fitting problem remains a challenge since we are still confined to extremely unevenly distributed depth samples collected along and near the ships, in which case numerous generic reconstruction algorithms generate unacceptable surfaces featuring abnormal depth fluctuations which are correlated with the trackline locations. Previously we reported the use a modified ODETLAP scheme, which integrates data-density-dependent smoothing into the reconstruction process, to generate surfaces which are free from such acquisition footprint. However, that scheme still suffers from terrain feature loss due to smoothing, and the reliance of human to decide appropriate smoothing factor. This paper aims to fix these two problems with a two-step ODETLAP procedure. The procedure first applies an accuracy-biased ODETLAP to complete the missing depth data from the given samples. After that, the vigorous depth fluctuations along the tracklines are removed by applying a smoothing-biased ODETLAP on the completed depth grid. To decide the optimal smoothing factor automatically, the procedure computes the areas of the individual bumps on the reconstructed surface. A surface suffering heavily from the artifacts has many small bumps but few big ones. Smoothing reduces such skewness. We find that for many datasets, the artifact is mostly gone when the coefficient of variation of the areas drops to around 1.3. Using that value to gauge the smoothing factor, the automated scheme successfully generates artifact-free seafloor surfaces within a limited error budget.