NavigationalDevices Used

At Sea

By: Reynaldo Thomas

Compass This is a magnetic needle which is mounted

on a pin so it is free to spin around.

The compass point always points north.

Compasses are mounted on gimbals which make the compass always horizontal when the boat moves up and down.

Echo Sounders/ Sonar Fishermen use it to find fish

It sends short pulses of sound through the water surrounding a fishing boat.

If the sound waves strike a shoal of fish they are reflected back to the boat.

The sound is detected by an operator in the boat.

Radar This uses electromagnetic waves to detect the

range, speed and direction of objects.

A transmitter emits the waves.

The waves then scattered when they contact an object.

A receiver detects the signal which is reflected back from the object.

The wavelength change slightly in the returned signal when the object is moving.

GPS (Global Positioning System)

A global navigation satellite system

Can be use by anybody worldwide

The GPS satellites broadcast signals from space

Any GPS receiver can obtain a three-dimensional location giving the latitude, longitude and altitude at a certain time.