Navigation

When u walk, cycle, or drive from one place to another, you plan your route first, and keep checking you are on course until you arrive at your destination. This process is called navigation.
Unless you know the way, you will also need navigational aids, such as maps and a compass. Accurate navigation is especially important at sea or in the air when no landmarks are visible.
The first, simple navigational aids, such as light houses, allowed early mariners to leave inland waters and navigate their way safely across the oceans.

Electronic navigation
Modern navigational aids use complex electronics and are very accurate. They detect radio signals sent from fixed radio beacons, and use them to work out the receiver's position. The most common and effective equipment is the global positioning system (GPS).
Automatic navigation
Many aircraft have an automatic, computerized navigation system. It consists of a GPS receiver and computerized maps. The aircraft's steering is automatically adjusted to maintain the craft on the correct course. Ships operate with similar systems.
Radar and sonar
Distant object are located with radar (radio detection ranging) and sonar (sound navigation ranging). Radar bounces radio waves off objects and detects the rejected waves. Sonar locates underwater objects with sound and echo waves.

Navigational aids

Navigational aids
For centuries, travellers have used navigational aids. The sextant, which measures the angle between too objects in the sky, such as stars or the sun, is still used by modern navigation.
Magnetic compass
The earth acts like a huge magnet, a pivotal magnetized compass needle will line up with the earth's magnetic north and south poles.
Gyro compass
A gyroscope is a device which remains stable while spinning. The gyro compass needle stays steady, even if it is tilted, making it ideal for accurate navigation.
Logs
A log consists of an underwater propeller, or rotator, which spins faster as the ship increases speed. A register counts the no. of spins, giving the distance travelled.

Use of navigation

Latitude and longitude
Maps and charts often show lines of latitude and longitude, imaginary lines crossing the earth's surface. Navigation use them to help locate their position and to chart their route. Latitude is a north-south division, drawn parallel to the equator.
Maps and charts
A map is like a picture of the ground, drawn from above. It shows feature on the ground such as buildings and hills. To navigate these can be matched up with feature on the ground. Positions checked using the lines of latitude and longitude.
Light and buoys
At sea, a system of visual aids helps vessels navigate safely. Light houses and lightships send out a unique pattern of flashing signals.
Buoys are floating markers. Their shape and colour indicate different hazards, such as the edge of a shipping lane or sandbanks.
Time line
11th century - Chinese mariners use simple compasses.
14th century - The portugese develop the astrolobe. Using the sun and stars, it helps locate a position on earth.
1569 - Flemish geographer Gerardus mercator (1512-94) publishes the first world map mariners use it to navigate.
1762 - British inventor john Harrison (1693-1776) wins a prize for building a chronometer, a mariner's clock.
1930s - Scottish SRobert watson - watt (1892-1973) develops the first practical radar system. Radars used extensively in world war II.