Automated Identification of Discrepancies between Nautical Charts and Survey Soundings

Giuseppe Masetti,Tyanne Faulkes,Christos Kastrisios

doi:10.3390/ijgi7100392

Abstract

Timely and accurate identification of change detection for areas depicted on nautical charts constitutes a key task for marine cartographic agencies in supporting maritime safety. Such a task is usually achieved through manual or semi-automated processes, based on best practices developed over the years requiring a substantial level of human commitment (i.e., to visually compare the chart with the new collected data or to analyze the result of intermediate products). This work describes an algorithm that aims to largely automate the change identification process as well as to reduce its subjective component. Through the selective derivation of a set of depth points from a nautical chart, a triangulated irregular network is created to apply a preliminary tilted-triangle test to all the input survey soundings. Given the complexity of a modern nautical chart, a set of feature-specific, point-in-polygon tests are then performed. As output, the algorithm provides danger-to-navigation candidates, chart discrepancies, and a subset of features that requires human evaluation. The algorithm has been successfully tested with real-world electronic navigational charts and survey datasets. In parallel to the research development, a prototype application implementing the algorithm was created and made publicly available.

Highlights

The content of a nautical chart is derived from data sources that may greatly vary in both quality and density [1,2]
It is common to have, in the same nautical chart, parts based on modern high-resolution hydrographic surveys coexisting with areas that have not been resurveyed since eighteenth-century lead-line surveys [3]
The International Hydrographic Organization (IHO) has created a standard vector format, named S-57, for official Electronic Navigational Charts (ENCs) that contain a set of data layers for a range of hydrographic applications

Summary

Introduction

The content of a nautical chart is derived from data sources that may greatly vary in both quality and density [1,2]. It is common to have, in the same nautical chart, parts based on modern high-resolution hydrographic surveys coexisting with areas that have not been resurveyed since eighteenth-century lead-line surveys [3]. The recent evolution of shipping has both widened and increased the hydrographic needs, with new harbors and routes established in areas that had never been surveyed [4]. The quality of a nautical chart depends on the surveys upon which it is derived but surveying for avoiding chart obsolescence represents a never-ending task

Methods

Results

Discussion

Conclusion