The hydrographic use of point feature objects to represent physical features of relatively significant spatial extent on an Electronic Navigational Chart can increase the risk of the hazard posed by such features being misinterpreted by mariners and potentially reduce the effectiveness of the ECDIS safety checking functions.
Australian Hydrographic Office (AHO) work to remediate the existing Australian ENC portfolio by encoding circular obstruction area features at the same location as applicable point features significantly reduces the risk identified by this safety issue. While the new area feature does not specifically reflect the shape and extent of Henry Reef, it nevertheless reduces the risk of the reef not being detected, both visually and when using the ECDIS. The challenges involved in charting all possible area features to the standard desired by users with specialised needs are significant. However, close engagement between such users and hydrographic service providers can help prioritise waters where better hydrographic detail may be required.
The information published by the AHO will serve to improve the general awareness among mariners of the potential risks of using over-scaled ECDIS displays near point features representing rocks, wrecks and obstructions. It will also aid to improve users’ understanding of chart accuracy. The submission of this publication to the IHO for consideration as an IHO standard provides an opportunity to raise awareness of this safety issue on an international level.
Safety action taken: The Australian Hydrographic Office (AHO) has undertaken work to remediate the existing ENC portfolio by setting up a dedicated project team to encode obstruction area features at the same location as underwater rock and obstruction point features. An initial search revealed approximately 2,200 such features affecting about 243 ENCs. The project commenced in December 2018 and involved creating an obstruction area the same size as the isolated danger symbol, while also retaining the latter. This means that within the ECDIS, the symbol behaves electronically in the same way as it looks visually. The project was completed in March 2019 and the issue was raised with the IHO.
In addition, the AHO has advised the ATSB that they have published a supplement to the Seafarers Handbook for Australian Waters (AHP 20) to address a number of misconceptions amongst mariners regarding the accuracy of bathymetry within Electronic Navigational Charts (ENCs) and the impact that accuracy should have upon route planning and conduct. The supplement also addresses the dangerous effects of over-scaled ECDIS displays near features such as isolated danger symbols (Appendix F). The content of this supplement will be fully incorporated as a new chapter into the new edition of the handbook (Edition 5), due for publication in 2019. The content has also been offered to the IHO for publication as an IHO standard.