Grid references

Grid references are an easy way of accurately locating any point on a map, and using them is an essential part of understanding topographic maps.

The grid on a map consists of two sets of lines, one set running north-south (called eastings) and one set running east-west (called northings). Each grid line is numbered; values of eastings increase from west to east, and values of northings increase from south to north (this should explain the names eastings and northings).

The following discussion and questions relate to an On-Line digital copy of a 1:25000 topographic mapsheet called "Ingliston". This mapsheet covers an area apporximately 7 km to the west of Bacchus Marsh.

To obtain the grid reference of any point on a map, first locate the easting immediately to the west of it, then estimate (in tenths of the distance between grid lines) how far the point lies to the east of this line. For example, the summit of Mt Darriwill has the grid easting 259 immediately to the west of it, and lies approximately 28mm to the east on the map (approximately * of the distance between grid lines 259 and 260). Thus the first half of its grid reference is 259. * of 1000 metres (the distance between each of the grids) is 750 metres. If we wanted to calculate the distance more precisely we could multiply 28mm by 25,000 to convert to ground units (equals 700 metres). Therefore the easting of Mt. Darriwill is 259700. The northing is calculated in the same way: ie. Mt. Darriwill lies immediately to the north of grid line 5831 but south of 5832. The map distance from the grid line to Mt. Darriwill measures 15mm (this converts to 15mm x 25,000 = 375,000mm = 375 metres ground distance). Therefore the northing of Mt. Darriwill is 5831375.

Coordinates for Mt. Darriwill are: E259700, N5831375.

Move the horizontal and vertical blue lines to find the grid references for any feature on this section of a topographic map.

Click here to go to Grid Reference Questions