I noticed this thing in a field to one side of the insanely steep path up to the top of the mountain here and decided to get a closer look. I am certain that it's a tomb, but the horse in the field with it is either very affectionate or insane. Either way it stopped me from getting really close to it.
The capstone projects from the slope horizontally and supporting stones can be seen below it. It probably measures around 1.5m square and 60 or 70 cms thick.
The large rock used to form the roof of a portal tomb or kist.
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This is an explanation of (and a bit of a disclaimer for) the coordinates I provide.
Where a GPS figure is given this is the master for all other coordinates. According to my Garmin these are quite accurate.
Where there is no GPS figure the 6 figure grid reference is master for the others. This may not be very accurate as it could have come from the OS maps and could have been read by eye. Consequently, all other cordinates are going to have inaccuracies.
The calculation of Longitude and Latitude uses an algorithm that is not 100% accurate. The long/lat figures are used as a basis for calculating the UTM & ITM coordinates. Consequently, UTM & ITM coordinates are slightly out.
UTM is a global coordinate system - Universal Transverse Mercator - that is at the core of the GPS system.
ITM is the new coordinate system - Irish Transverse Mercator - that is more accurate and more GPS friendly than the Irish Grid Reference system. This will be used on the next generation of Irish OS maps.