MAPPING THE OCEANS

Sonar plays the major role in surveying the ocean floor-taking measurements on the depth and form of features on the seabed. Sonar is based on the principle of the echo: Sound waves are bounced to the ocean bottom and back, with distance determined by the time this process takes.

In multibeam sonar, the sound source and receiver are built into the hull of the ship, and the sonar system scans a wide area as the ship moves along. In sidescan sonar, the sound originates in a towed source.

Things to look out for

Look at a map. What do you see?	You see symbols and a key.
	Symbols stand for bigger things, like mountains, streets, or even streams.
	Symbols are so very small. Maps and globes can’t show it all.   A city might be a little dot.
Just use the symbols and the key, reading maps is fun and easy!

The maps have small pictures on them which show the kind of countryside and even where different things, such as coffee, grow around the world. Each map is very small compared to the size of the real world, so these pictures are signs to give you the general idea rather than showing exactly where everything is.

It’s obvious, as a rule, what most of them mean but some are still explained. National flags can be also placed near most of the capital cities. Names of the countries and capital cities are both in capital letters.

Date: 2015-04-20; view: 1144