Francis Bradleyexplains the essentials of map-reading and compass work
Every walk in a new environment - be it a new city, country, mountain or bog - requires advance planning. All factors have to be considered - weather, length of route, fitness, age. Of course, you have to be able to find your way around. For this you will need some map-reading skills and basic use of a compass.
The most popular map scale used in Ireland is 1:50,000 (two centimetres to one kilometre) in the Ordinance Survey Discovery Series. There are also more detailed maps, 1:25,000 (four centimetres to one kilometre), available for selected areas. Essentially, the more detail available the better.
When examining a map, take note of features such as steepness of route - are the contour lines close together? Terrain - bog, open grassland, forest, rivers and streams, walls and rights of way. Are there well-defined tracks, or will you be breaking new ground? All these factors will influence your decision on whether a route is suitable, and how long it might take. Also, the rule of thumb for estimating time required is to allow one hour for every four to five kilometres, plus one minute for every 10m height gained. This relates to the minimum time necessary to complete a route, based on a presumption of reasonable fitness.
However, calculations should be based on the speed of the slowest person, and a "correction" of 25-50 per cent should be added to take account of breaks, photographs and delays.
The main uses of a compass are: getting a bearing from a map and using this information to walk in a particular direction (on a known bearing), identifying features, positioning the map to conform to the location (orienting the map) and identifying your position.
The most popular compass is the Silva-type compass. This is usually a transparent plastic structure having a base plate with a direction arrow and scales and a rotatable circular housing for the magnetic needle. In order to take a bearing from point A to point B on a map, the compass is placed on the map with the edge of the base plate lined up on the intended direction of travel from A to B, ensuring that the direction arrow is pointing in the desired direction of travel. Holding the base plate in position, rotate the circular housing until its arrow points to grid north on the map. This is known as a "grid bearing" and a further adjustment is necessary, which includes magnetic variation. The Earth's magnetic North Pole moves slightly each year and this variation is indicated at the side of most maps.
Magnetic north "pulls" the compass needle away from true north, so a small adjustment is needed to correct this. While walking, regularly check that the compass needle is still correctly aligned with the north arrow in the circular housing. Be aware that the direction the magnetic needle is pointing can be influenced by metal objects - put the compass on a flat non-metallic surface, bring a mobile phone close to it and note what happens to the needle. Watches, cameras, metal buttons, zips are some of the items that can cause errors, so move the compass away from possible sources of interference.
Plan your route and make sure to leave details with a family member or a friend.