Course correction is the chain that turns a chart course into one you can actually steer on the compass: from the true course (rwK) through variation and deviation to wind and current. This guide walks through the chain step by step in NauticCalc — forwards (rwK → steering course) just as well as backwards.
Prerequisites
- rwK for the leg from the chart or the passage plan
- Variation for the position (Variation)
- A maintained deviation table for the compass course
- If needed: wind and current data for the correction
Step 1: Enter rwK
Open course correction and take the leg course from the chart. Check briefly whether it matches the planned track — a swapped waypoint is easiest to spot here.
Step 2: Apply variation
Enter the variation for your position (from WMM or chart). The app computes mwK = rwK ± variation — rule of thumb: east subtract, west add. Check the sign; it is the most common source of error in the whole chain.
Step 3: Deviation
Take the value for this course from your deviation table. This gives MgK = mwK ± deviation — the course your ship's compass shows.
Step 4: Wind and current
Now apply the corrections as needed: wind by strength and angle, current from the plan or via current correction / the current triangle. The result is — depending on the task — the steering course or the COG.
Step 5: Check at sea
Check roughly via GPS along the way whether you stay on the track line. If the run drifts off, adjust the estimate for current and wind instead of steering on "blind". The whole chain also works offline.
Common mistakes
- Wrong sign applied for variation or deviation
- Lumping variation and deviation together
- Forgetting the wind and current correction even though both have a noticeable effect
- Confusing the forward and backward calculation (steering course wanted vs. COG wanted)
Read next: Blog: course correction step by step · Current correction