relating+map+and+ground

outdoors home > navigation = = toc =Relating map and ground = A map on its own is of limited use. The ability to transfer information between the map and the ground, however, is a vital skill for navigation.

One way of making it easier to transfer this information is be orientating the map so it is aligned to match the terrain - ie a feature on the map and the feature it represents on the ground lie in the same direction from you. This is called //setting// the map. (sometimes called //orienting// the map, especially in the USA).

Although there may be times when it necessary to stop, consciously set the map and compare features on the map and on the ground it is preferable to frequently compare features on the ground with those on the map and keep track of position on the map (sometimes called "thumbing" as the thumb of the hand holding the map can be moved to point to the last known position).

setting a map (MCofS) [|staying on course]

Setting the map by features
If you are sure of your current position this involves rotating until the features on the ground match those on the map. Either stand still and rotate the map in front of you, or hold the map in front of you (eg with grid north facing away from you) and rotate yourself (keeping the map in the same place relative to you).

If you are unsure of your current position you will need to match features on the ground and map in at least two directions (ideally about 90 degrees apart). Take care to avoid making the features "fit" where you think you might be; if you cannot see features from your position that the map suggests you should be able to, you are probably not where you thought you were.

Forests and wooded areas tend to change most - these cannot be relied upon for setting a map. Contours are the most permament features and are the best ones to use to set a map in a hilly area. Linear features (called **handrails**) are often useful when orienting a map by features.

When moving keep the map "set" in the correct orientation - even if that means the writing on the map is "not the right way up"; it will help identification of features. Setting a map using a compass is covered here.

setting (orienting) a map:

Setting a map using contour features (aka by "terrain association")
In remote areas man-made features may be absent; these cannot be use to set the map so the shape of the terrain has to be used. The five characteristics of the terrain that should be assessed, then compared with contours on the map, can be remembered with the mnemonic SOSES. These same aspects can be useful when trying to relocate. In this situation it is important to try to avoid convincing yourself you are where you think you might be rather than systematically analysing features around you on the ground and comparing those with what is on the map. An options here is to look around you and write down information about your surroundings before you try to find these on the map.
 * Shape || General form/outline at the base of the feature (eg circular, elliptical) ||
 * Orientation || Is the feature parallel to your line of sight, perpendicular, or somewhere in between? ||
 * Size || Horizontal size at the base of the feature (width or length) ||
 * Elevation || Compared with other features nearby and, possibly, your own height (the latter is less reliable if you are distant from the feature) ||
 * Slope || Steepness and shape (convex etc) ||

<span style="font-family: Verdana,Geneva,sans-serif;">Ridgelining
<span style="font-family: Georgia,serif;">This is a technique to help appreciate the layout of hills. <span style="font-family: Georgia,serif;">Using a brown or red pen mark the ridges joining high points - this will includes spurs coming off ridges.

<span style="font-family: Verdana,Geneva,sans-serif;">Streamlining
<span style="font-family: Georgia,serif;">Is the equivalent technique for highlighting streams and other watercourses with a blue pen.

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<span style="font-family: Verdana,Geneva,sans-serif;">Setting a map with sun or stars
<span style="font-family: Georgia,serif;">**If you are planning to go somewhere where this skill is likely to be needed then obtain expert tuition beforehand and practise until you have mastered the skill.**

<span style="font-family: Georgia,serif;">The movement of the sun can be used to determine the direction of north, as can the pole star (in the northern hemisphere). These techniques will not work when the sky is too cloudy.

<span style="font-family: Georgia,serif;">Be aware the sunrise and sunset are NOT always due east & west respectively (only on the equinoxes will this be the case). <span style="font-family: Georgia,serif;">The closer the date to winter/summer solstice the further south/north (respectively) of east and west will the sun rise and set (this is because of the 23.5 degree tilt of the eath's axis of rotation)

<span style="font-family: Georgia,serif;">see this page for setting a map with a compass

<span style="font-family: Verdana,Geneva,sans-serif;">Following features
<span style="font-family: Georgia,serif;">It may be possible (and is relatively easy to do when this is the case) for follow a handrail (linear feature) that appears on the map and ground. The most obvious example of this is a path (but beware that the presence of a right of way on an OS map does not necessarily indicate there will be a path visible on the ground). Other such features that can be used for navigation include walls, streams, valleys and ridges.

<span style="font-family: Georgia,serif;">The position along the linear feature may be determined by looking out for nearby spot features that are passed. These are sometimes called <span style="color: #ff0000; font-family: Georgia,serif;">tick features, because you find them on the map and "tick" them off as you pass them on the ground. They are also called "collecting features".