Knowing how to provide a grid reference is a handy skill – it lets people know exactly where you are and references are often used in search and rescue situations.

Grid references are used to identify specific locations on a map and anyone with the same map can quickly understand exactly where you are referring to.

On the Topo50 maps there is a series of evenly spaced horizontal and vertical lines called ‘eastings’ and ‘northings’.  These grid lines divide the map into a set of numbered 1km squares. At a scale of 1:50,000, each square is 2cm by 2cm and the numbers increase from west to east and from south to north.

To quote the local grid reference for Mt Sunday on the Topo50 BX18 map, follow these steps:

1. Note down the number of the map, e.g.  BX18.
2. To determine your easting, locate the vertical gridline to the left of the point (Mt Sunday) and read the grid value labelling the line: 29. Estimate (or measure) to a tenth of a grid square the exact location reading from west to east: 8.
3. To determine your northing, locate the horizontal gridline below the point. Read the grid value labelling the line (top, bottom or middle of the map): 76. Estimate (or measure) to a tenth of a grid square the exact location reading from south to north: 2.
4. Quote the grid reference: BX18 298 762.