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Sailing Directions

Admiralty Sailing Directions are intended for use by vessels of 12 m or more in length. They amplify charted detail and contain information needed for safe navigation, which is not available from Admiralty charts, or other hydrographic publications. They are intended to be read in conjunction with the charts quoted in the text.

Sailing Directions are kept up to date by supplements published at intervals of 1 ½ to 2 years, each new supplement cancelling the previous one. In addition important corrections, which cannot await the next supplement, are published in Section IV of the weekly editions of Admiralty Notices to Mariners.

The following items are the most important subjects for Sailing Directions. Buoys are generally described in detail only when they have special navigational significance, or where the scale of the chart is too small to show all the details clearly.

Chart references in the text normally refer to the largest scale Admiralty chart but occasionally a smaller scale chart may be quoted where its use is more appropriate.

Except for submarine exercise areas, details of firing, practice and exercise areas are not mentioned in Sailing Directions, but signals and buoys used in connection with these areas are sometimes mentioned if significant for navigation. Attention is invited to the Annual Notice to Mariners on this subject.

Wreck information is included where drying or below water wrecks are relatively permanent features having significance for navigation or anchoring.

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Navigational Charts

It is known that for many years Great Britain and Russia have been main chart suppliers in the world. A chart is one of the most important publications for safety of navigation. Parts of the sea or of the ocean are given in it with the indication of depth, character of ground, coastline, dangers and wrecks. There are such notions as: geographical elements and navigational elements. All these elements have special marks and symbols.

According to scale charts are subdivided into Ocean charts, General charts, Plans and Large Scale charts. The Natural Scale is the proportion, which any measurement on the chart bears to the actual distance.

There are three Projections: Mercator, Gnomonic and Stereographic. While reading charts we must know definite amount of conventional abbreviations and signs which are grouped under titles: the coastline, coastal features, topography, natural and artificial features, control points, units of measurement, adjectives – characteristics, harbours, buildings – as prominent marks, different objects, lights, buoys and beacons, radio and radar, fog signals, dangers, various limits, soundings, depth contours, quality of the bottom, tides and currents, principal foreign terms.

Every chart begins from the correction date; dimensions of the plate and also of chart datum as well as heights and drying heights are introduced. Figures on the land show the Heights in feet above High Water Springs. At the same time the datum to which the soundings are reduced true is the level of Mean Low Water Springs. The Datum is the level of the sea for places where there is no tide.

Charts are generally drawn on the True Meridian, if not, a True Meridian is given on the Chart. Longitudes are referred to the Meridian of True Meridian Greenwich. Direction shows us that all Bearings are true and are given from seaward. The Bearings are referred to the True Compass, and given in Degrees are reckoned clockwise from 000° (North to 359°). The Annual Change in Magnetic Variation is shown at certain positions on the curves. A positive (+) prefix denotes an annual increase, and negative (-) prefix – and annual decrease in the variation.

While working with charts it is necessary to pay due attention to cautions and notes. It is of common knowledge that charts are always published by the Hydrographer of the Navy, London.

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