Datum points are metal poles (with a specific letter on a sign), that were used as reference points during live firing when artillery was used on the moor. Today, a lot of these poles are missing or damaged in some way, and this one - "R" - is missing has fallen over but is still intact. The actual post is about 10m away in a hollow (see reference point).
There used to be a nearby Datum Point (W) on Black Ridge (at about SX5960 8595) but it also no longer standing and I was unable to find any base or pole amongst the peat hags.
Please Note: This is a Military Training Area on which live firing and other pyrotechnics may be used. The area is generally open public access. One of the safety rules for public access is:- Do not, (and ensure that children do not) approach, touch or pick up any metal objects lying on the ground. Please obey all byelaws and locally posted information concerning times when the area may be closed. These may be physical barriers, flags or lights.
This cache complies with the DNPA agreement for geocaching - http://www.dartmoor-npa.gov.uk/visiting/vi-enjoyingdartmoor/geocaching