# Nautical Charts. Types of Scales

April 11, 2017 SorinMStamate

### Nautical Charts. Types of Scales.

The Nautical Charts showing the Earth’s surface or a portion thereof on a plan, in a certain proportion (scale) and with deformations subject to mathematical laws.

Such a chart must meet the following conditions:

1. The quick and easy insertion of the geographical coordinates of a point;

2. The angles on the chart to be equal to those on the surface of the Earth;

3. The rhumb line and the great circle can be drawn by a straight line.

On a chart are shown a lot of elements using abbreviations, symbols, explanatory notes, warnings, namely:

a. The coast line;

b. The seabed topography;

c. The nature of the seabed;

f.  Natural and artificial navigation landmarks;

g. The magnetic declination and magnetic anomalies;

h. The elements of the tide and currents;

i.  Places for anchorage;

j.  The boundaries of the different regions;

k. Fairway.

The nautical charts are divided according to the scale in four categories:

1. General charts:

– Drawn at a scale between 1: 500,000 – 1: 5,000,000

– Are represented large oceanic basins and are used for:

·         Study of the navigation conditions;

·         Preparing the sea passage;

2. Route charts:

– Drawn at a scale between 1: 100,000 – 1: 500,000

– Used for navigation at deep sea or near the coasts;

– On which are represented the most important elements for navigation;

3. Coast charts:

– Drawn at a scale between 1: 50,000 – 1: 75,000;

– Used for navigation close to land, among islands, fjords, straits;

4. Plans:

– Drawn at a scale between 1: 5,000 – 1: 25,000;

– Used for operating in ports, roads, gulfs and bays.

For navigation purposes are used the following cartographic projections:

1. Mercator’s projection:

– With Rectangular Canvas;

– And the rhumb line appears as a straight line;

2. Gnomonic projection:

– Used for the navigation on the great circle;

3. stereographic projection:

– Used for navigation in the polar regions.

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