Map Reading

The number of people who walk regularly but shy away from basic map reading is surprisingly large. Certainly anyone who walks alone in unknown or mountainous areas should have some map reading and navigational skills, but even in familiar territory navigation is easy and can be fun.

Buy a few maps of your favourite areas and learn to use them .

Using a map

A map is a two dimensional model of the landscape. Map reading is the ability to look at a map and process it into a mental picture of the landscape, an important skill in selecting and following a route.

Scales.

Maps come in a wide range of scales. The two most popular maps of the British isles used by hill-walkers are:

  • 1: 50,000, on this scale 2cm on the map = 1km on the ground
  • 1: 25,000, on this scale 4cm on the map = 1km on the ground

Obviously the 1: 25,000 provides more information but you will need more maps to cover the same area.

1: 50,000 are readily available for all parts of the British Isles and 1: 25,000 are available for popular walking areas.

Grid References.

So what are the vertical and horizontal lines on the map?

The British and Irish grids divide the British Isles into squares, each square is 100km x 100km and identified by a letter. (e.g) most of the Mournes is within grid letter J and much of the Sperrins within grid letter H
Each area within the bounds of each grid letter is further divided into 1km squares by grid lines. These are the numbered and marked lines we see on the map. They run North-South and East-West.

So how do we get a grid reference?

  • First determine the letter which defines the 100km grid. 
  • This letter can be found on the map legend and in this case is H-see top left hand corner of map.
  • The Eastings run across the map in this case from 45-53
  • The Northings run vertically on the map-in this case from 93-100
  • H4796 is the four figure grid reference for Balix Hill -not very accurate it covers a fairly large area 1km x 1km
  • A six figure grid reference reduces the error and gives a reading within 10m x 10m. The grid reference for Balix Hill would become H475962-much more accurate.
  • An eight figure grid reference is accurate to 1m x 1m-but of course in this case the grid reference must be taken very accurately.

Six figure grid references are probably the most accurate possible with a 1: 50,000 map

Eight figure grid references are easier to obtain from a 1: 25,000 map.

Using a 1: 25,000 map of the Sperrins an eight figure grid reference can be readily estimated using the 1: 25,000 scale on a Silva Walkers Compass

Corick Mountain has twin tops, the higher at 430m has a grid reference C76070367

Setting a map.

When using a map it is good practice to keep it set, a map is the right way relative to the ground when set.
A map can be set:

By using a compass to align the grid lines to the North or using familiar or known ground features so that the directions of these features on the map and on the ground are the same.

Compare the equivalent map set N-S, with arrow pointing south.