Module 7 of 17
Charts & Publications
Reading nautical charts, symbols, chart correction, and navigational publications.
Nautical Charts
A nautical chart is the mariner's map of the sea. It shows depths, coastline shape, navigation marks, hazards, and other essential information. Charts are drawn to Mercator projection, with True North at the top and compass roses for measuring bearings.
Charts come in different scales: a small-scale chart covers a large area (e.g., an ocean passage chart) while a large-scale chart shows a small area in great detail (e.g., a harbour approach). Always use the largest scale chart available for the area you are navigating.
Key Points
- Charts show depths, coastline, marks, hazards
- Mercator projection — True North at top
- Small scale = large area (passage charts)
- Large scale = small area (harbour charts, most detail)
- Use the largest scale chart available for your area
Tip: Think of it like zooming in on a map: large scale = zoomed in (shows more detail). Small scale = zoomed out.
Chart Symbols and Abbreviations
Charts use hundreds of standardised symbols defined in INT 1 (also known as Chart 5011 in the UK). Key categories include: depth contours and soundings, rocks and wrecks, buoys and beacons, lights, anchorages, traffic separation schemes, and land features.
Blue tint indicates shallow water (drying or very shallow). White or no tint is deeper water. Green tint shows land areas that may dry. A depth sounding of 3.2 means 3.2 metres below Chart Datum. A drying height of 1.5 (underlined) means 1.5 metres above Chart Datum.
Key Points
- INT 1 (Chart 5011) — reference for all chart symbols
- Blue = shallow water, White = deeper, Green = drying land
- Soundings = depth below Chart Datum
- Underlined values = drying heights above Chart Datum
- Asterisk with purple 'flare' = light
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