Workflow of Shallow-Water Hydrographic Mapping: Acquisition to Post-Processing

Regina Lionheart, Oceanography

This project focuses on the workflow used in shallow-water hydrographic mapping, from shipboard acquisition to post-processing techniques. Multibeam data was collected within the urban waters of Lake Washington and Puget Sound. During data acquisition, positional accuracy was uniform and variation in trackline overlaps were monitored. After acquisition, the raw data was then imported into Teledyne CARIS HIPS and SIPS for generation of several alternative workflows in the production of base surfaces and variations in cell size resolution. This investigation focused on workflow alternatives for data used in analytical techniques specifically for change detection of base surfaces over time. The information may serve as an aid to navigation, or data which produces final results from methods which are transparent and reproducible. Additionally, the workflow included the use of the ArcGIS software by ESRI for conversion of all base surfaces to raster data models of similar dimension, allowing for quantification of change using simple map algebra functions. Data product usability and reproducibility within a GIS environment were explored. Subtracting the swath angle layer from the more detailed CUBE layer created an entirely new surface that displayed the numeric as well as spatial pattern of differences between layers. The workflow process has resulted in an objective and quantified commentary on analytical techniques in shallow-water hydrographic surveying. In the race to document more of the coastal ocean, both visual and analytical outcomes of survey data are required. This work identifies useful methods to help insure that survey outcomes are both understandable by the public and reproducible by others.