Hi, welcome to what will be a series of blogs on Map Reading and Navigation. The aim of this series is to introduce you to the map & compass in a simple and non-technical way. The series will slowly lead you through from understanding what a map is telling you to being able to navigate reasonably proficiently.
The knowledge you gain here is just the foundation, you will need to practice the skills you learn over and over again. I always recommend that the first time you go out to navigate a route, take an experienced navigator with you. They will be able to guide, assist and help correct any errors that you make. Once you have mastered the art of navigation, the world is your oyster.
For many people, when they open a map, they feel as though they are staring into deep space. They are just bewildered by the lines, colours and symbols that adorn the page. To some extent, this is true. A map is a story book, but unless you can read what is written, it just as well be ‘Double Dutch’.
So before we even think about route planning or navigation, we will start by learning to ‘read’.
The first thing is to select the correct map. In the UK, the national mapping agency is the Ordnance Survey (OS) who product a series of different scaled maps. The most common of these are the 1:25,000 scale Explorer and the 1:50,000 Landranger maps. For walking I strongly recommend the Explorer map, and this is the one I will always refer to.
Every map has a Legend which explains what all the lines, colours and symbols mean. It is worth taking a few evenings to study the map and the Legend and get familiar with the various notations.
Exercise: Select a small area near you and identify what every single line and symbols means. Think about what you expect to see, then go out and try to find it. As you walk around, constantly compare the map to what you can see around you.
Whilst you were studying the map and learning the meaning of the various notations, you may have seen that the entire map was covered with a grid of faint lines. These grid lines are 1km apart and form part of the larger National Grid. This system allows any point in the entire country to be identified.
Every point on a map has a unique reference code like a postcode. Each 100km x 100km square is identified by two letters. The 100km square is identified in each corner of 1:25k & 1:50k maps and at boundary changes.
Each 100km square is then divided into 10km x 10km squares each identified by two numbers. Then each 10km square is divided into 1km x 1km squares identified by a further two numbers.
The 1km squares can then be subdivided into 100m x 100m squares each identified by a further two numbers. This brings the total up to two letters and six numbers and is referred to as a 6-figure grid reference.
The vertical lines are known as the eastings because they are numbers towards the east and are always given first. The horizontal lines are called the northings because they are numbers towards the north and always come second. Remember – along the corridor (eastings) then up the stairs (northings).
It is important to note that the grid reference relates to a square, not a point. The accuracy can be increased by using 8-figure grid references which relate to 10m x 10m squares, when using the 1:25k scale maps.
Aids To Taking Grid References
The roamer scale on the top and side of a compass can be used to help you get an accurate grid reference. Another device that I highly recommend is the roamer grid reference tool from ShavenRaspberry, an absolute timesaver.
Exercise: Select an OS Explorer or Landranger map of your local area. Identify some of the features and landmarks near to your, such as your church, footpaths and bridle way, and different road types. Select some features and work out the 6 or 8 figure grid reference for their positions. remember eastings first then northings – or along the corridor then up the stairs.
Regardless of scale, the grid lines on an Ordnance Survey map are spaced 1km apart. Therefore, a rough distance can be calculated by counting the number of squares between two points. Another useful dimension to remember is the diagonal of the grid square measures 1.5km
On a 1:25000 map 4cms equates to 1km, 1cm = 250m. As most compasses have a centimetre scale, this is another way of measuring distance. For the 1:50,000 map, 2cms equates to 1km, 1cm = 500m.
Another useful measuring device is a length of string which is used to follow a curved route then held against the scale at the bottom of the map.
In Map Reading & Navigation – Part 2, we will be looking at planning a short walk, understanding relief and look at pacing.