Module 10 - Chartwork
Waypoints and GPS Navigation
A waypoint is a position defined by latitude and longitude, used to mark turning points or destinations on a passage. Modern GPS and chart plotters navigate between waypoints and display bearing, distance, and cross-track error.
While GPS is invaluable, you must always be able to navigate without it. Batteries fail, equipment breaks, and GPS signals can be unreliable or subject to spoofing. Chart plotters should confirm — not replace — traditional chartwork.
At Coastal Skipper level, understand GNSS limitations: Horizontal Dilution of Precision (HDOP) affects accuracy; satellite geometry matters; signals can be blocked by terrain or rigging. Always cross-check an electronic position with at least one independent source — a visual bearing, depth sounding, or radar range.
Key points
- Waypoint = a Lat/Long position used for navigation
- GPS gives bearing, distance, XTE (cross-track error) to waypoints
- Always have a paper chart backup
- Cross-check GPS position against visual observations
- Plot GPS positions on the paper chart regularly
- HDOP and satellite geometry affect GPS accuracy
Continue studying Chartwork
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