Electronic Navigational Charts
Overview of ENCs in Australia
All ENC published by the AHO are included in the AusENC Service and are also available through the commercial services provided by IC-ENC Value Added Resellers (VARs) and PRIMAR. The AusENC service includes distribution and updates of charts covering Australia, Papua New Guinea, Solomon Islands, Australian Antarctic Territory and New Zealand waters.
More information on the AusENC service can be found here
AusENC can be used on any system that supports the IHO S-63 format. There are a wide range of systems including ECDIS, ECS, radar, VTS and GIS systems that can use ENC data. Some of the compatible systems are listed on the AHO website - Australian Hydrographic Office - IHO S-63 Original Equipment Manufacturer (OEM)
Use of ENCs
The ENC coverage of Australian waters is 100 per cent. The use of raster navigational charts (RNC), when ENCs are available, is not permitted in Australia.
In Australian waters, vessels are required to navigate on up to date and appropriately scaled ENCs when using ECDIS or Electronic Chart Systems (ECS).
An appropriately scaled ENC is one of a suitable scale for the navigational task at hand, noting that the chart’s scale determines the level of detail provided. Therefore, the largest scale charts produced should always be used.
Small scale charts depict large areas. They are suitable for overall voyage planning and ocean transit purposes. Small scale charts have fewer details about aids to navigation, dangers, coastal features, and infrastructure, particularly where larger scale charts exist. Significant depth detail is omitted.
Small scale charts are generally unsuitable for navigation in areas less than 30 metres depth, areas adjacent to the coast or close to navigation hazards. Small scale charts contain information about the limits and identity of larger scale charts. Whether in electronic or paper format, small scale charts are neither intended nor suitable for coastal navigation.
Large scale charts should be used when navigating close to the coast, reefs, and other navigation hazards. These charts cover smaller areas and provide more detail about depth, dangers, aids to navigation and coastal features. Generally, Australian ENCs provide continuous coverage at a scale of 1:90,000 (ENC) or larger when navigating within 24 nautical miles of land or major offshore features, except in remote areas.
How to purchase AusENCs
AusENC can be obtained from AusENC distribution agents listed on the AHO website: Australian Hydrographic Office – Distribution Agents.
AHO published ENC can also be obtained in services provided by IC-ENC VARs http://www.ic-enc.org/.
How to sign up for and receive updates to ENCs
Any ENC service is accessed via a subscription to the desired ENC cells which is tied by a permit which is unique to a particular navigation system. Updates are included for a subscription’s duration. More information on how to install and use AusENC can be found at - https://hydro.gov.au/factsheets/FS_AusENC-Installing_updating_and_renewing_the_AusENC_Service.pdf.
Dangers of over-scaling ENCs
Use of over-scale display of an ENC may be dangerous in certain circumstances. There is a mistaken belief that zooming in allows for greater accuracy – however, this is not the case. Zooming in beyond the intended maximum display scale may be misleading and dangerous, particularly for ‘Isolated dangers of depth less than the safety depth’. Over-scaled ENCs will show a ‘jail bar’ pattern across them and/or display an over-scaled warning notice.
Every ENC is compiled at an intended maximum scale. At this scale the maximum level of detail is revealed, while zooming out will progressively reduce the level of detail. None of this affects the accuracy of the chart. Zooming in may reveal a new, larger scale ENC, but this too has limits, and a point will be reached where there is no point zooming in further.
Please refer to the Mariners Handbook for Australian Waters (AHP20) for further information.