Page 185 - NAVAL SCIENCE 3 TEXTBOOK

UNIT

Marine Navigation

avigation is the art and science by which mariners find a vessel's position
N and guide it safely from one point to another. Most of you would know
how to guide yourself, or a watercraft, by following a magnetic compass needle.
The problem is finding your location in the first place. This is the navigator's first
job: to locate the vessel exactly on the Earth. The navigator can then recommend
a course to be steered in order to arrive safely at the destination.
To find Ollt where we are 110W, we must locate ourselves in relation to some-
thing else. For instance: your desk is 20 feet from the back door and directly in
front of the teacher's desk. Or your hOllse is on the corner of Elm Street and
\·Vestern Avenue. Using a road map) we can say that the town of Jefferson is Oil
Highway 26,15 miles south of Watertown.
We have now used a tool that is important in locating places: a map. In this
unit, we will talk abollt maps of the Earth, particularly, maps that show on a flat
surface the locations of places important to the mariners of the world. The type
of map lIsed to navigate on the water is called a IInlltieni chnrt. The charts we
will talk about may be defined as "pictures of the navigable waters of the Earth."
Charts are what the navigator uses when plotting courses and finding positions
of his or her vessel. The navigator cannot refer to a highway. a crossroads. or
towns. There has to be a wa), of locating the vessel on the ocean. The following
chapters will describe how this is done.