Use the accompanying map to establish coordinates for points in and around Markethill and District.
Use this tool to get the map coordinates of any place in the Markethill area. (If you cannot see the tool, download and install Adobe's Shockwave Player, available at http://get.adobe.com/shockwave/)
Use the UP, DOWN, LEFT, RIGHT buttons to move the map. The coordinates for the location at the centre of the target circle on the map will appear.
The coordinates you read from this map are approximate. They are accurate to between 30 and 100m.
Coordinates are given here in two ways: WGS84 coordinates and Irish Grid coordinates.
WGS84 (World Geodetic Survey 1984) is the default standard used by satellite global positioning systems (GPSs. The latitude is given first (in °degrees, 'minutes and "seconds), followed by the longitude (in °degrees, 'minutes and "seconds). "N" is for North and "W" is for West.
Irish Grid coordinates are composed of an inital letter followed by 6 numbers. The letter denotes a 100km2 area. The area on our map overlaps the H square and the J square. The first 3 numbers are the Northings, or hundred metres north of an origin point; the second set of three numbers are the Eastings, or hundred metres east of an origin point. The origin point for the H square is a point in the Atlantic, 200 000m West and 300 000m South of the H square. The origin point lies 300 000m West and 300 000m South of the J square.
Example. The Grid Reference for the Old Courthouse in Markethill is H961404. It is at a point 2 961 00 metres (296.1km) North and 3 404 00 metres (340.4km) East of the origin point for the Irish Grid.
The Irish Grid map is based on measurements made before the invention of more accurate satellite measuring techniques. Readings of latitude and longitude from Irish Grid maps need adjusted slightly to agree with the WGS84 standard. Ordinance Survey recommend adding 23.4m to Irish Grid Northings and subtracting 49m from Eastings to bring Irish Grid readings into general good agreement with WGS84 readings. This approximates to adding 0.75 seconds to the Latitude and subtracting 2.7 seconds from the Longitude.
The Old Courthouse, Markethill is located on the Ordnance Survey Northern Ireland map at
Latitude N 54° 18' 0", Longitude W 006° 31' 20".
Using the correction above, this becomes
Latitude N 54° 18' 1", Longitude W 006° 31' 17".
An actual WGS84 reading (accurate to 6m) was
Latitude N54° 18' 3", Longitude W 006° 31' 19"