The Tellurometer distance-measuring instrument. (EDM)

The instrument consisted of a Master unit and a Remote unit (like the one sitting on the concrete pillar), a carrying case for each unit, two wooden telescopic tripods, two 12V battery packs and two accessory cases containing the radio handsets etc.

 In the first version only the Master unit could carry out the distance readings whilst the Remote unit served as a ‘mirror’ to redirect the radio wave back to the Master.

In later versions, each unit could be switched between Master and Remote, so enabling measurements to be taken both ways.

The one in the photos, taken in Kenya in 1959, is of the latter type, whilst the one used in the Seychelles was the first model.

In the Seychelles early in 1958, Mick Dyall and Trevor ‘Bill’ Powell on detachment from 13 FSS made the first measurement ‘in anger’ from Bird Island to Silhouette,
a staggering 53 miles (85 Km),

 unbelievable for that period in time.

 A real survey revolution.