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 navigation. Parts of the sea or of the ocean are given in it with the indication of depth, character of ground, coast line, 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 chats, 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 corrections 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 refered 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 an 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.

II. NOTES:

wreck - остовы разбитого судна, останки крушения

General chart - генеральные карты

Large Scale chart - крупномасштабные карты

conventional abbreviations - общепринятые сокращения

prominent marks - приметные ориентиры

soundings - измеренные глубины

dimensions - размеры

chart datum - нуль карты

bearings - пеленги

be reckoned - подсчитываться

clockwise - в направлении часовой стрелки

cautions - предостережения

curve - кривая линия

III. ANSWER THE FOLLOWING QUESTIONS:

1. What countries are the main chart suppliers in the world?

2. What information is given in the chart?

3. What projections are used for the chart?

4. What abbreviations must be known?

5. Why is it necessary to pay due attention to cautions?

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