Reading a Map

Map Reading and Navigation 🏆

Course 1 · Chapter 1 · Reading a Map: Scale, Symbols and North

A map is a small, flat picture of a large piece of ground, drawn so that you can measure it and find your way across it. Before you can navigate you must be able to read one: how much ground it covers, what its symbols mean, and which way is north. This chapter covers those three things. Later chapters add grid references, contours, the compass, bearings, route planning and what to do when the weather turns.

What a Map Shows

A map is a selection, not a copy. The mapmaker leaves out most of what is on the ground and keeps what a walker needs: paths, roads, rivers, buildings, woods, and the shape of the land. Because the choice is made for you, you must know what a map includes and what it leaves out, such as a path that has become overgrown or a fence added last year.

Scale

The link between a distance on the paper and the same distance on the ground.

Symbols

Small pictures and coloured lines that stand for real features. The legend (or key) explains them.

Direction

Most maps are drawn with north at the top, and mark north with an arrow or the grid lines.

Date

Every map is out of date the day it is printed. Check the edition or revision date in the margin.

Scale

Scale is written as a ratio. On a 1:50,000 map, 1 unit on the paper is 50,000 of the same unit on the ground. So 1 cm on the map is 50,000 cm, which is 500 m, on the ground. A larger scale number means a smaller, less detailed map of a wider area.

Scale	1 cm on the map	Typical use
1:25,000	250 m	Walking and detailed route finding (many walkers' favourite)
1:50,000	500 m	Walking and general travel
1:250,000	2.5 km	Planning a long journey by road

The conversion is always the same: multiply the map distance by the scale number, then change the units. The quick way is to learn the two common cases by heart: at 1:25,000 every 4 cm is 1 km, and at 1:50,000 every 2 cm is 1 km.

# ground distance = map distance x scale number
scale   = 50000          # a 1:50,000 map
map_cm  = 7.5
ground_cm = map_cm * scale     # 375,000 cm
ground_m  = ground_cm / 100  # 3,750 m
ground_km = ground_m / 1000   # 3.75 km

Use the scale bar Most maps print a scale bar in the margin. Lay the edge of a piece of paper along your route, mark the distance, then hold it against the bar. This also copes with the paper shrinking or being printed at the wrong size, which a ratio alone cannot.

Symbols and the Legend

You do not need to memorise every symbol, but you should know the main groups and always check the legend for the rest. Colour does a lot of the work. The pattern below is common on walking maps, but the exact colours and symbols vary between publishers and countries (check the legend of your own map).

Colour	Usually means
Blue	Water: rivers, lakes, the sea, and often streams and ponds
Green	Woodland, forest or other vegetation
Brown	Contour lines (the shape of the land; see Map Reading and Navigation 3)
Black	Buildings, boundaries, names and many paths
Red or orange	Main roads, and sometimes rights of way or access land

A path on the map is not a promise A dotted line shows that a path existed when the map was surveyed. It may be faint, flooded or gone. Rights of way and access rules also differ between countries, so a path being drawn does not always mean you may use it.

Finding North

A map has a fixed direction. On most maps the top edge is north and the grid lines run north-south and east-west. That is grid north. The north that a compass needle points to is magnetic north, and it is slightly different, and the difference changes over the years and from place to place. Chapter 4 explains this in detail; for now just remember that the map, the compass and the real north pole are three slightly different things (check the declination diagram in your map's margin).

# orient a map without a compass
find a linear feature you can see (a road, a river, a wall)
turn the map until that line on paper points the same way
check the features beside you match the map around you
your position is now somewhere on the map beside them

Reading a Map in Order

Experienced walkers read a map the same way every time, and the habit stops mistakes. Work from the big picture to the detail.

Step	Ask
1. Edition	How old is this map? What has probably changed?
2. Scale	How much ground does one centimetre cover?
3. Legend	What do the symbols and colours mean on this map?
4. North	Which way is north, and is the map oriented?
5. Features	Which large, obvious features (rivers, roads, woods) can I match to the ground?

Challenges

Exercise 1

Convert these map distances to ground distances: 6 cm on a 1:25,000 map, 6 cm on a 1:50,000 map, and 3.2 cm on a 1:50,000 map. Give each answer in metres and in kilometres, and say why the first two answers differ.

→ Solution

Exercise 2

Take any printed or online map. Write down its scale, its edition or survey date, and the meaning of five symbols from the legend. Then name two things on the ground that the map might not show.

→ Solution

Exercise 3

Write a short program or spreadsheet formula that turns a map distance in centimetres and a scale number into kilometres. Test it with 8 cm at 1:25,000 and 8 cm at 1:50,000, then add a second function that does the reverse: how many centimetres on the map for a given ground distance.

→ Solution

Quick Reference

Scale: ground distance = map distance x scale number
1:25,000: 1 cm = 250 m, 4 cm = 1 km
1:50,000: 1 cm = 500 m, 2 cm = 1 km
Colours: blue water, green woodland, brown contours, black detail
Always check: the legend and the edition date
North: grid, magnetic and true north differ slightly

Coming next Chapter 2 introduces grid references: how to turn a point on the map into a short number code that anyone with the same map can find.