Before you start
Gather the appropriate supplies and review the specific equipment manual.
- Chart legend
- GPS and display settings
- Local survey notes
Step-by-step instructions
Understand coordinate datums
Latitude and longitude are tied to a geodetic reference such as WGS 84. Older charts may use a different datum.
Read the chart notes
Check source chart datum and whether corrections or offsets are supplied for electronic or paper use.
Review display settings
Confirm the plotter and imported waypoint files use compatible coordinates and chart sources.
Compare known references
In safe water, compare position to properly charted landmarks and independent observations rather than assuming the display is exact.
Plan conservative margins
Avoid close navigation to hazards if source data is old, survey confidence is low or positions disagree.
Safety note
Never correct an uncertain position by an arbitrary chart offset and then assume all hazards are safe.
Key takeaway
A precise GPS fix can still sit on an imprecise or mismatched chart.
Keep this job on your maintenance schedule
Save the topic as a maintenance task, choose a due date or engine-hour target, and record future service. Free and stored on your device.
Add to my maintenance plannerThis guide is for general education. Follow your equipment manufacturer’s instructions, current navigation guidance and applicable marine safety standards. When uncertain, use a qualified marine professional.