This is the second of two articles on chartwork, aimed at OOW candidates. The first of these articles is linked below and contains a note regarding upcoming changes to the ‘chartwork and tides’ syllabus. We recommend that you read that article before continuing with this one.

Recommended reading: **NP735** (IALA Maritime Buoyage System**), NP5011** and **NP5012** (Symbols and abbreviation used on admiralty charts, guide. to symbols used on ECDIS), **NP294** (How to keep Admiralty products up-to-date)

**Buoyage system and direction of buoyage**

The explanatory notes on a paper chart will state a buoyage region (IALA A or B). The direction of buoyage is shown on the chart as a symbol; an arrow pointing between two coloured circles.

At a point where the direction of buoyage changes there may be two such symbols, for example when going round an island. The direction of buoyage is:

**Towards**a rivers source**Into**a harbour**Clockwise**around continents

**Compass rose**

Most charts will have multiple compass roses. Magnetic variation **(the angular difference between true north and magnetic north)** is given for the point at the centre of the compass rose, on the first of January of the given year. The outer ring shows true north; the inner ring shows magnetic north. The annual rate of change is also be given, so that from the stated variation and the annual rate of change we can find the present variation. To find the magnetic variation for a location between two or more compass roses it is sometimes necessary to interpolate.

**How to find variation**

The value given for variation is for the first of January of 2020; in the image above, 1 degree West. For the first of January 2023 we should apply three years worth of change: 3 x 11’ E = 33’ East. This rounds to half a degree E, making the resulting variation half a degree West. For convenience, round to the nearest half degree.

Magnetic variation is sometimes given in magenta ink for some positions, without an accompanying compass rose. Some charts show isogonals (lines of equal magnetic variation) and magnetic anomalies, where they exist, are shown.