This stone is unmarked on the OS and lies to the east of the tomb here on the edge of a private road.
The 'Private Road' sign had a message reading "Grattan Club members meet at full moon 666" ... a reference to the Hellfire Club..
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From the R113 in south Dublin follow the signs for the Wicklow Way and park in the car park at O150 245. There are some steps in the car park that lead onto the track above. Follow this 'private' track and keep looking into the trees on your left around 100m along.
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.