What are nautical charts used for?

A navigational chart shows relevant data for the crew of any vessel on their travels, such as coastlines, facilities, ports,

A navigational chart shows relevant data for the crew of any vessel on their travels, such as coastlines, facilities, ports, etc. In the past these documents were only available on paper, but nowadays digital versions are widely accessible. In this article we will explain nautical charts and the information contained in them.

What is a nautical chart?

What’s a nautical chart? A recurring question from those not used to plough the seas. Much more than a maritime “road map”, for someone at the helm having access to a nautical chart means knowledge on sea areas, ports, coastlines; it may show depths of water and heights of land, natural features of the seabed, navigational hazards, locations of natural and human-made aids to navigation like buoys, information on tides and currents, etc. The purpose of a nautical chart is to give the sailor updated information to safely travel the seas, preventing any risks from running aground and avoiding restricted navigational areas.

Nautical chart providers
The crew of any vessel on their travels, such as coastlines, facilities, ports… Pixabay photo.

What sort of information do nautical charts provide?

They provide essential information for all kinds of vessels. The relevance of this information is directly related to the navigation equipment on board. Charts typically contain the following information:

Positioning data:

Reticle.

Magnetic variation.

Details of the coastline.

Topography.

Soundings, or water depth measurements.

Landmarks

Radar conspicuous objects.

Maritime radio stations. Radionavigation and radiodetermination stations.

Range of radar stations.

Hyperbolic navigation grids.

Route finding data:

Coastline.

Sounding and depth contours.

Dangers to navigation.

Currents and tidal streams.

Names of ocean bottom features.

Names of ocean divisions, bays, and waterways.

Names of land features.

Ports, roads and anchorages.

Recommended tracks, traffic lanes and waterways.

Restricted traffic areas.

Leading marks.

Bridge or other clearances (vertical and horizontal).

Safety and ease of navigation:

Chart datum.

Nature of bottom.

Bridge or other clearances (vertical and horizontal).

Various limits (fishing areas, customs boundaries, harbour limits, etc.).

Military artificial features.

Maritime radio stations. Radionavigation and radiodetermination stations and various other stations such as signal stations, pilot stations, etc.

Harbour facilities.

Places for clearance by Customs Authorities.

Notes, warnings, remarks.

Digital nautical chart or paper nautical chart?

Nautical charting may take the form of charts printed on paper or electronic navigation charts so both forms can be found, though the phaseout of traditional paper products is reflected in the industry. On the topic of which form should a vessel equip, the International Convention for the Safety of Life at Sea (SOLAS Convention) states that all ships shall have:

  • Nautical charts and nautical publications to plan and display the ship’s route for the intended voyage and to plot and monitor positions throughout the voyage; an electronic chart display and information system (ECDIS) may be accepted as meeting the chart carriage requirements of this subparagraph. Back-up arrangements to meet the previously stated functional requirements, if this function is partly or fully fulfilled by electronic means.
  • So, the vessel should be equipped with an Electronic Chart Display and Information System (ECDIS), support computers and a solid power source. A set of paper nautical charts should be available as a precaution.

For the safe functioning and navigation, situational awareness is the key to use all this information, whether it is electronic in nature or not. Situational awareness describes a process of gathering complete objective data about your immediate environment and using it to make the best decisions that you can. Seeing an area at a proper scale is key to the navigational process.

digital nautical chart providers
There are two types of electronic charts: Raster Navigational Charts and Electronic Navigational Charts.

Types of electronic nautical chart

There are two types of electronic charts that an ECDIS can display: Raster Navigational Charts (RNCs) and Electronic Navigational Charts (ENCs) otherwise known as vector charts.

A raster chart is an electronic picture of a paper chart obtained through a detailed scanning process and therefore it shows exactly what is originally represented on a paper chart. A vector chart is digitally processed with lines, dots, areas and allows the user to click on different features, such as a light or buoy, to retrieve additional information not available in paper or raster charts.

All ships are required to carry nautical charts either published by the corresponding administration or with the official seal to display their intended route and monitor their position. There are also commercially published charts, some of which may carry additional information of particular interest but these are not official.

Scanned charts (RNC)

A raster navigational chart, or RNC, is a scanned reproduction of a paper chart. It is a computer-based system which uses charts issued by, or under authority of, national hydrographic offices. Its contents are officially sanctioned and based on international standards. Paired with automatic continuous electronic positioning, it provides an integrated navigational tool.

Vector charts (ENC)

An electronic navigational chart or ENC is an official database created by a national hydrographic office for use with an Electronic Chart Display and Information System (ECDIS). Only ENCs can be used within ECDIS to meet the International Maritime Organization (IMO) performance standard for ECDIS.

ENCs are coded and compiled following international regulations and as such the World Geodetic System 1984 Datum (WGS 84) must be the reference for ENCs positions. They are periodically digitally updated.

Updating the nautical charts

The updating process for scanned or vector charts consists of periodical updates applied to the cartographic data. The process can take place via a data file that can be transmitted through radio or other formats like a disk.

Nowadays it is even more frequent that these updates arrive via satellite or once the ship is docked at port. ENC service providers offering digital updates or via web can be also appointed.

To conclude, at Suisca Group, your maritime partner with more than 30 years of experience, we offer everything a ship needs on a stopover. If you are looking to buy nautical charts, place your confidence in us and our team of experienced professionals that will provide you with technical assistance and specialized advice. Suisca Group’s own Representaciones & Charts is an approved supplier of the UKHO’s ADMIRALTY nautical charts. At Suisca Group, we are proud suppliers of these products and services.