Navigation is the art of knowing where you are on the surface of the globe. It is an ancient art that has largely been replaced with technology in recent times.
As late as the 20th century, celestial navigation relied on the observer being able to see the sun, the moon, or stars at exactly the right time.
Latitude can be measured by taking sightings on the sun or stars, although it is mostly done today by GPS hardware that relies on the locations of satellites.
Simple interference in the form of fog, cloud, mist, or being busy when deciding was to be taken, could cause a 24-hour delay in getting an accurate position.
Longitude can be measured best with a good chronometer, so you can relate your present position to the reference position from which longitudes are measured.
Longitude may also be measured by careful observation of the moon and using tables, but this is an unreliable method, especially when a ship is moving.
In 1735, John Harrison built his first marine chronometer (Number One), designed to win the award of the British Board of Longitude for an accurate time keeper.
In 1759 John Harrison completed his fourth chronometer (Number Four), which would eventually gain him the Board of Longitude's prize for accurate time keeping.
In 1761 John Harrison's portable chronometer (Number Four) was successfully tested on a trip from Britain to the West Indies and back, proving itself at sea.
The quadrant was an early navigational instrument with limited use.
The sextant was an early navigational instrument with limited use, but it was able to give remarkably accurate results when latitude needed to be found.
A compass is needed to make sure a boat sails in the right direction, once it is out of sight of land, although radar and GPS equipment are more reliable.
One of the drawbacks of the old magnetic compass was that it tended to swing around when used on a small rocking boat. Oil damping fixed this.
One of the drawbacks of the old magnetic compass was that it relied on a magnetic field that was not uniform in its direction from place to place.
Edmond Halley experimented with the use of charts of magnetic deviation, the difference between true and magnetic north, to find longitude around the world.
Between 1783 and 1824, the national Ordnance Survey of England, mapped all of Britain, except for the eastern part of England and north-west Scotland.
The main role of the people we call Australian explorers was to work across Australia, surveying the series of triangles to map the continent by triangulation.