grid references

All Ordnance Survey maps (and many others) are criss-crossed by vertical and horizontal grid lines. If they could be drawn on the ground, they would be exactly one kilometre apart. On the map, grid lines are 4 centimetres apart on the 1:25,000 scale; 2 centimetres apart on the 1:50,000 scale. The lines are blue or black, depending on the type and age of map being used.

Grid lines are so-called after the national grid whose origin lies at a point in the Atlantic Ocean to the south-west of the Scilly Isles. Each grid line has a two-digit number shown where it meets the edge and at intervals across the body of the map.

Giving a grid reference for the Challenge (Two Letters, Four Figures)

To give a grid reference for a whole grid square:

  1. Find the two 'grid letters' for the square in the map key (e.g. TQ)

  2. Imagining a capital 'L' bounding your square, find the two-digit number for the downstroke of the 'L' which forms the western (or left) side of your square (e.g. 31)

    grid ref diagram1

  3. Then find the two-digit number for the across stroke of the 'L' which forms the southern (or bottom) side of your square (e.g. 25)

  4. You will then have the grid reference needed for submitting Challenge squares (e.g. TQ3125)

Submit Challenge squares

Giving a grid reference when reporting a path problem (Two Letters, Six Figures)

When reporting a path problem a more precise grid reference is needed. We give this by adding an extra figure to each of the two-digit numbers found above:

  1. Find the two 'grid letters' as above (e.g. TQ)

  2. Estimate how many tenths across the square (eastwards or to the right) the problem is located. Add this figure to the two-digit number for the western (or left) side of the square (e.g. If the problem is located seven-tenths across the square the extra figure will be 7 - giving 317)

    3. grid ref diagram 2

  3. Estimate how many tenths up the square (northwards) the problem is located. Add this figure to the two-digit number for the southern (or bottom) side of the square (e.g. If the problem is located four-tenths up the square the extra figure will be 4 - giving 254)

  4. You will then have the grid reference for reporting the problem (e.g. TQ317254)

Report a path problem to the Ramblers' Association