What this is about
Course correction means taking a course from the chart to the steering compass — accounting for variation, deviation, wind, and current. Without a clear order you quickly swap signs or skip a step.
This article walks through a practical sequence for sailors. Notation (rwK, mwK, MgK) is explained in rwK, mwK, and MgK: the course chain.
Step 1: Chart course (rwK)
On the chart you read the true course (rwK) — planned direction over the ground relative to geographic north.
- Connect waypoints, note the chart course
- Quick sanity check: coastline, depth contours, traffic
Step 2: Apply variation (rwK → mwK)
From rwK to variation-corrected course (mwK):
mwK = rwK ± variation
Common mnemonic: East least, West best — always verify the sign on the chart or WMM.
→ What is magnetic variation? · Calculator: Variation
Step 3: Boat deviation (mwK → MgK)
Your compass does not show “pure” magnetic north — the boat influences it:
MgK = mwK ± deviation
Deviation comes from your deviation table (compensation). Without it, the chain is weak at this step.
Step 4: Wind and current (MgK → COG / steering course)
From compass course (MgK) to course over ground (COG) you add allowances:
- Wind (lee) — from wind strength and angle
- Current — from set and drift or the current triangle
For current only, see Current correction. The full workflow is Course correction.
Step 5: Steering course on the compass
You end with the course you read and steer on the magnetic compass — or the COG you want to hold over ground, depending on the problem (forward or backward).
Tip: State the task clearly: “I have rwK and want MgK” vs. “I have MgK and want COG”.
Typical mistakes
| Mistake | Effect |
|---|---|
| Variation and deviation swapped | Course wrong by several degrees |
| Current doubled or forgotten | Track off the chart line |
| Outdated variation | Systematic error over the leg |
| Wind only “by feel” | Lee under- or over-estimated |
Offline on the bridge
Course correction, variation, and current are core calculators in NauticCalc — they run without internet. GPS and logbook are local too; live weather and online tides are optional (BYOK).
→ Sailing without internet · Offline hub
Bottom line
Course correction is not one formula but a chain. If you walk rwK, mwK, MgK, and allowances in a fixed order, you steer more safely — especially with no network.
Read next: Course correction in the app · Current triangle · Download