First there was the theodolite then the electronic theodolite which enabled automated data collection and took the error out of reading the instrument.

Distance measurement took a step forward when EDM (Electro-magnetic Distance Measurement) was introduced. To measure with EDM a reflector was needed at the point being measured in order to bounce the I/R beam back to the instrument.

When the electronic theodolite and the EDM were combined into a single instrument it was called a Total Station. As technology developed it was found unnecessary to use a reflector to achieve the required amount of reflected beam and so the reflectorless total station, or REDM, was born.

The benefit of the REDM unit is that it only required one person to operate it, whereas previously one person was needed on the instrument and one on the reflector.

There are still times, especially with topographical surveys, that a reflector is still needed, for example, measuring heights across a field, where the surface may consist of grass or other vegetation. In these situations, a special total station is employed that tracks the movement of the reflector automatically. On the back of the reflector is mounted a remote control panel which enables the surveyor to type in detail codes thereby controlling the total station remotely. This system again allows the survey to be carried out by a single person, although a well trained Alsatian is useful to prevent the total station from 'disappearing'!