Prerequisites
- Magnetic compass on board (compensatable)
- Current variation for your area (Variation)
- Quiet berth or calm sea for compensation
Step 1: Prepare compensation
Read your compass manufacturer’s instructions. You need access to the compensation screws and space to run eight cardinal/intercardinal headings (0°, 45°, 90° …).
Step 2: Run courses and record
For each heading:
- rwK from the chart (or passage plan)
- Apply variation → mwK
- Read MgK on the compass
- Deviation = difference between mwK and MgK (keep sign convention consistent)
Record everything in a table — on paper or directly in NauticCalc.
Step 3: Maintain the table in NauticCalc
In the app under course correction / deviation table:
- Enter course ranges or individual headings
- Check plausibility (e.g. a few degrees max on a well-compensated compass)
- Save — the table is used in course correction
Step 4: Update regularly
After refits (electronics, speakers, engine work) or when errors appear: re-compensate or adjust the table.
Common mistakes
- Confusing variation and deviation
- Measuring only one heading
- Keeping an old table after changes on board
Read next: Course correction guide · Variation