Before you start
Gather the appropriate supplies and review the specific equipment manual.
- Current chart data
- GPS status screen
- Compass and visual references
Step-by-step instructions
Check the displayed fix
Look for loss of satellite fix, position jumping and unusual uncertainty indications.
Check datum and chart source
Ensure consistent chart datum and up-to-date chart coverage.
Compare independent observations
Match the plot with safe visual bearings, depth trends or radar where available.
Review antenna and connection status
Diagnose visible warning messages without touching energized wiring.
Use safe margin
Increase distance from hazards until the source of any discrepancy is understood.
Safety note
Never navigate narrow or shallow water relying on a single questionable position source.
Key takeaway
Good navigation compares multiple sources instead of trusting one dot.
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.