Flier finder

The “Flier finder” algorithm is dedicated to one of the major identified problem: the quite common presence of anomalous data in the finalized gridded bathymetry delivered to the hydrographic branches (aka “fliers”). This represents a major concern since, when fliers are found, there is considerable time and effort required to remove them, as it involves re-computation and re-finalization of the grids, which can take several days (or longer) to accomplish with the additional disadvantage that the output is no longer the authentic field submission. This algorithm contributes to detect fliers as early as possible in the quality control process.

Its initial implementation scans gridded bathymetry and flags abrupt depth changes as per user-set criteria, as shown in figure (white “lassos” encircle the anomalous grid data). Several algorithm modifications have also been testing (e.g., by including the evaluation of additional statistic layers provided by a CUBE DTM).

Feature validation

The “VALSOU to grid check” and “feature scan” algorithms have their focus on the required agreement between gridded bathymetry and submitted feature files, as well as the adherence of those feature files to current specifications. Wrecks, rocks, and obstructions should have appropriate representation in the gridded bathymetry with regards to position and least depth. It is a common situation at HBs to receive surveys with hundreds (or even thousands) of features that need to be manually checked against the grid to ensure agreement, and also to ensure proper attribution.

This process can be a massive time sink and, having a monotonous nature, makes it perfectly suited for automation. The developed algorithms scan the gridded bathymetry and feature files to ensure this agreement, and that the attributes of the feature are set per current version of the NOAA Hydrographic Survey Specifications and Deliverables (HSSD) manual. An example of the agreement we wish to observe is shown in figure.

QC Tools