Wednesday, April 11, 2007

Differences Between a Charts and Maps


Let's Clear Up The Confusion!


A chart, especially a nautical chart, has special unique characteristics including a very detailed and accurate representation of the coastline, which takes into account varying tidal levels and water forms, critical to a navigator. It's important to store your maps and charts in a waterproof case!

A map, on the other hand, emphasizes land forms, including the representation of relief, with shoreline represented as an approximate delineation usually at mean sea level.

A chart is a working document. It is used to plot courses for navigators to follow in order to transit a certain area It takes into account special conditions required for one's vessel, such as draft, bottom clearance, wrecks and obstructions which can be hazardous. Way points are identified to indicate relative position and points at which specific maneuver such as changing courses, must be performed.

A map on the other hand is a static document which serves as a reference guide. A map is not, and can not be used to plot a course. Rather it provides a predetermined course, usually a road, path, etc., to be followed. Special consideration for the type of vehicle is rarely a consideration. Further, maps provide predetermined points-road intersections-to allow one a choice to change to another predetermined direction.

Charts provide detailed information on the area beneath the water surface, normally not visible to the naked eye, which can and is very critical for the safe and efficient navigation.

Maps merely indicate a surface path providing no information of the condition of the road. For instance a map will not provide information on whether the road is under repair (except when it is a new road) or how many pot holes or other obstructions it may contain. However the driver is able to make a visual assessment of such conditions.

Since we need to have an underwater's eye view - let's get those charts out and use them!

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