What to know for Charts and Position Basics
Use a chart or chart plotter to recognise hazards, depths, and the approximate position of the boat.
Chart symbols, depths, hazards, latitude and longitude, and simple position awareness. This module is mapped to the published course boundary for Essential Navigation and Seamanship Revision and written as an independent revision aid, not official training material.
Key Points
- Depths are charted from chart datum
- Latitude and longitude give position
- Symbols and abbreviations must be checked in the chart key
- Electronic charts still need human checking
Last reviewed: 6 July 2026 by Compass Revision curriculum review
Source notes
Revision checks
Use these checks before moving on. If one feels vague, reread the module and compare it with the linked official source before treating the topic as learned.
Core topic tags: chart symbols, depths, latitude and longitude, position awareness.
Key Points
- Can you explain: Depths are charted from chart datum?
- Can you explain: Latitude and longitude give position?
- Can you explain: Symbols and abbreviations must be checked in the chart key?
- Can you explain: Electronic charts still need human checking?
Source notes
Common mistakes
Most assessment and real-world errors come from misreading the situation, skipping a simple check, or treating a memory aid as a substitute for judgement.
Use this section as a pre-test: if you can explain why each mistake is risky, you are closer to usable knowledge.
Key Points
- Reading charted depth as actual depth
- Ignoring drying heights and rocks
- Zooming electronic charts without checking detail