Rockbrook 2 is a solitary stone that sits in a fence about 100m from the road in a paddock. It seems to be in line with the possible alignment at Rockbrook (County Dublin).
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A little diversionary stop to see if I could get a better look at this stone. The house next to the paddock where this stone stands is currently empty with decorators doing stuff there so I wandered across to the stone.
It is about 1.4m tall (if straightened) and leans to the south slightly.
Take the R116 south from Dublin and turn left onto the R113. Rockbrook 2 is in a field to the left after about 200m. Take the next right after Rockbrook 2 to find Rockbrook 1.
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.