In this more detailed chart all the reefs are shown (and not symbolised) and greater detail is supplied regarding water depth. Note that the Indian Ocean extracts show only a few of the small reefs (the areas in green) within the lagoon, and most of these are shown as symbols (stars). This extract from a chart of the Timor Sea has a great deal more information about the water depths around Ashmore Reef than the two extracts above from an Indian Ocean chart. Note that the level of information supplied about depth is far greater than on the first image this is because small changes in depth in shallow water can be a hazard to shipping, whereas in deeper water it is not as critical. See the section about maps being reproduced at different scales in the Marginalia Section. The second extract is the same as that shown in the first extract – it is shown here in a larger format for ease of reading. The numbers indicate known depth for an individual spot and the dotted line is an indication of lines of equal depth - generally called bathymetric contours (or isobaths) to distinguish them from land contours. This includes information about the seabed depth below the surface of the water. The first extract is an example of the level of information that charts show over great expanses of ocean. ![]() These are extracts from Australian charts which cover part of the Indian Ocean and include Ashmore Reef. The chart images used here are with the permission of the Australian Hydrographic Service for more information regarding Australian marine navigation charts please visit their website Marine navigation charts (also referred to as nautical charts) are produced at a vast variety of scales – depending on the information available and the nature of the area being mapped. A key factor in this was that they also needed specialist information to aid navigation. In the twentieth century, with the arrival of flight, a convention developed that maps which were specifically made to aid aeroplane navigation would also be called charts. a mountain or a headland), compass roses and text notes (examples of text notes are ‘area usually covered in fog’, ‘strong tides occur in spring’ etc). This information included such things as water depth, location of lighthouses, significant coastal features (e.g. main roads or inland towns) would not be shown.Īnother difference was that charts had specialist information which aided navigation, especially navigation out–of–sight of land. cliffs ⁄ headlands or lighthouses) would be shown, while features which are important to maps (e.g. Also, land features which would be an aid to navigation (e.g. submerged rocks) were shown in as great a detail as knowledge and the scale (size) of the chart would allow. In particular, features which could be dangerous to ships (e.g. However the chart was more likely to show great detail about the water and the water's edge, with little information about the land – the exact opposite of a map. Both would map the coastline and its features. When people started making maps 5,000 years ago a distinction gradually emerged regarding maps of land and maps of the sea/ocean.įor the land they were called maps and for the sea/ocean they were called charts. Explaining Some Jargon – The Difference Between Maps and Charts air navigation charts are usually produced by a country’s Airforce plus a civilian agency which is responsible for civilian air traffic control and regulation.Īlso, navigation charts typically have well defined standards which are strictly adhered to.marine navigation charts are usually produced by a country’s Navy and possibly also by civil defence bodies and ⁄ or port management authorities.Like topographic maps, charts are typically produced by government mapping agencies: Specialist knowledge is usually required to read charts. ![]() Navigation Charts combine aspects of topographic, general reference and thematic maps and are produced as navigation aids for ships, boats and aircraft.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |