Compass Deviation Calculator
Model compass deviation from a manual value or coefficient card, then convert cleanly between compass, magnetic, and true headings.
🚤Quick Scenario Presets
⚙Heading And Deviation Inputs
📊Deviation Constants Grid
📘Reference Tables
| Compass Hdg | Typical Deviation | Magnetic Output | Use Case |
|---|---|---|---|
| 000 C | +0.8 deg | 000.8 M | North leg check |
| 090 C | -0.4 deg | 089.6 M | Cross-channel |
| 180 C | -1.7 deg | 178.3 M | Return south |
| 270 C | +1.2 deg | 271.2 M | Westing leg |
| Variation | True-Mag Gap | At 10 nm Track | Priority |
|---|---|---|---|
| 2 deg | 2 deg | 0.35 nm drift | Moderate |
| 5 deg | 5 deg | 0.87 nm drift | High |
| 8 deg | 8 deg | 1.40 nm drift | Critical |
| 12 deg | 12 deg | 2.10 nm drift | Severe |
| Coefficient | Term | Effect Pattern | Interpretation |
|---|---|---|---|
| A | Constant | Uniform offset | Permanent bias |
| B | sin(H) | Fore/aft field | Asymmetry |
| C | cos(H) | Athwartship | Beam influence |
| D,E | 2H terms | Quadrantal error | Hull iron effect |
| Target True | Var / Dev | Compass Steer | Back Bearing |
|---|---|---|---|
| 060 T | 4W / 1E | 063 C | 243 C |
| 115 T | 7E / 2W | 120 C | 300 C |
| 202 T | 3E / 1W | 200 C | 020 C |
| 318 T | 9W / 2E | 311 C | 131 C |
Bus of kompaso is magnetic mistake that bad affects the drive of the kompaso. It is made up of the difference between the real magnetic course and that erroneous that shows the instrument. This mistake comes because of magnetic interferenco that devias the needle to other electromagnetic influence instead of directly to real north.
Here happen because of attributes of the ship self. Samples about causes that that cause are the motorbloko kabladon either others feraj metallic objects. Also radios carboys and cells can generate magnetic fields that bothers the kompaso.
Why a Ship’s Compass Can Be Wrong
Metallic structures in the ship cause deviation. Here belongs steel of the body surges or topmasts. Even bank of paint in cabinet or conductors in cabinet can that happen.
On big ships even good can it cause. Magnetic bus comes of local fields beside electrical devices or feraj materials. They twist the teran magnetkampon at the kompaso.
Hence bus depends of particular course. The steel twists around it according to kurŝanĝoj. Because of that chart of bus point correction for every magnetic course of kompaso.
You combines it with variation of chart for find real course.
On modern fibroplastaj ships bus less commonly surpasses 2 grades. Even so it ranges of +2 until -2 grades according to the course of the ship. Bus of +2 grades wants to say that kompaso add two.
For instance for real magnetic course of 124 it shows 126. If you want to follow 240 grades magnetic you must use kompasan course of 243 grades. Here the bus for 240 is +3 grades.
Specialist swings the kompaso for estimate difference between the naval orientation of it and real magnetic. One mode reduce bus are Flinders-bars. The ajustisto compensate those sturbaloj.
They identify the field virtually the ship would not exist. You can self estimate local bus. For sample well lay it on the ground.
Use portatlan kompaso for markadi north south east and occident. Later turn the ship and note the differnces.
