Australia will be changing from the geodetic datum in use since 1966 to a new coordinate system. This will mean that all existing maps of Australia will be inaccurate by approximately 200 metres, and that digital data purchased from Auslig will soon shift by a similar distance.

This change is brought about as a result of the widespread use of GPS receivers. Users of GPS are often disappointed when they try to relate their reported position to a measurement on a map. The discrepancy is caused not only to the deliberate error introduced by the US military to confound the rest of the world, but also by the different coordinate systems being used. The change in the Australian measurement system will address the second of these causes.

The talk will outline the history of measuring position, discussing the meaning of the terms latitude and longitude, and show how the different coordinate systems in current use in Australia and in the GPS system relate to one another.