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.