Reading nautical charts

Australian navigable waterways feature thousands of buoys, beacons, and lights which mark dangers,  identify safe water and limits of dredged channels. From a chart you can learn where sandbars are located, obtain water depths and tide levels, find prohibited anchorages, see where navigation aids are located as well as confirming your compass and direction for the area you plan to go boating in.

Nautical Charts, paper and electronic are produced in Australia by the Hydrographic Office, a department of the Australian Defence. They are distributed to licenced chart agents such as Boat Books around Australia.  Australian charts are prefixed AUS and British charts BA and NZ for New Zealand.

Charts for an Australian passage can be selected from  a chart index produced by the Hydrograhic Office and generally have to be ordered in advance of when they are required.

Australian Index of Northern Charts AUS 5000
Australian Index of Southern Charts AUS 5001

State Maritime Authorities also produce local boating maps for their coastal regions.

Australian charts are kept up to date by the issue of Notice to Mariners, a Hydrographic Office publication available to any boating enthusiast. Urgent information is broadcast by coastal stations, often as a “Securite” message.

Chart Basics

Meaning of chart symbols

Scale

Nautical charts come in different “scales,” the ratio of a given distance on the chart to the actual distance. When you are sailing in open waters, you’ll probably use a small-scale chart (1:100,000 or higher) that covers a large area. When you are close to shore, and more at risk from shoals and other dangers, your large-scale chart (1:20,000 to 1:80,000) will provide more detail over a smaller area. The AUS 200 (Sydney Harbour Chart) has a scale of 1:25, 000.

Distance

Charts use the “nautical mile” (1.15 statute miles), the length of one minute of latitude. Travelling one nautical mile in one hour is a speed of 1 knot.

Chart notes

Located around the outside of the chart and in the lower left corner, is the chart’s edition number and publication date, title and scale of the chart.

Nautical charts whether paper or electronic are an important piece of safety equipment. They provide information you need to know about your boating area. If you are planning a trip to a location you’ve never been before, reviewing the area chart will provide you with valuable local knowledge.