The map is the essential tool of the sport and accordingly is an orienteer's most vital piece of equipment. Although it is possible to orienteer on almost any map, it is much more enjoyable to use maps made specifically for orienteering. Such maps are accurate and detailed, and are prepared on a human scale This means that terrain and features are mapped so that what appears on the map are the features that a human, moving through the area, sees readily. For example, boulders that are waist high would usually appear on orienteering maps. Most people are familiar with the Ordnance Survey maps, but orienteering maps are special maps which differ from Ordnance Survey maps as follows:Grid lines run North-South only and indicate Magnetic North. These lines (known as north lines) are parallel lines drawn running from magnetic south to magnetic north and spaced between 200 to 500 meters apart on the map. On the example shown here, they are drawn in black. The reason that the north lines on orienteering maps are not drawn pointing to true north is because orienteers often use compasses to orient the map (to magnetic north, not true north) as the angle between magnetic north and true north (the declination) varies widely in different parts of the world. It has thus become a standard to provide a series of reference lines on the map so that it is easy to use an orienteering compass to take a bearing.
They are at a much larger scale and therefore allow much more detail to be shown. In fact, anything permanent on the ground which might act as a control site or aid navigation is normally mapped. For example, natural ground features (pits, knolls, crags etc.), vegetation features (thickets, clearings etc.), and man-made features (fences, walls, drains, buildings etc.) would usually be mapped. Usually the scale of orienteering maps is 1:10,000 or 1:15,000 - this means that a distance of 1cm on the map represents 100m or 150m on the physical terrain.
The colours, signs and symbols are unique to orienteering maps. Usually a key or legend appears on each map, but after a few events the colour and symbol definitions become second nature. The colours on orienteering maps are used to depict vegetation according to its density or runability. Yellow areas are treeless, white areas indicate wooded area where you can run, and dark green signifies very thick vegetation, often impenetrable.
Contours are much more detailed, usually appearing at vertical intervals of 5m.