Map Reading & Navigation – Part 5

Today we will be looking at more advanced navigation techniques.  These are designed to get you to and from your target location when the visibility is poor or there are a lack of good features.  They include a means of using potential navigational errors to your advantage, or ensuring you leave a summit safely and make you way back down.

Aiming Off & Attack Point

Aiming-off is a navigational technique used in poor visibility. It improves your chances of reaching your destination, when that destination is situated on, or close to, a line feature.

In the example shown the aim is to get to the summit Trig Pillar from the end of the track. If a bearing was followed directly to the summit, there is a good chance that we would miss it completely. By intentionally ‘aiming off’ to intercept the fence, somewhere in the aiming-off zone, we have eliminated the risk of error.

aiming off

Because this does not lead directly to the summit, we need to establish an attack point.  This is a clear feature from which a final attack can be made on the destination.  In this case it is the end of the fence.

From this point we are approximately 200m from the summit so a direct bearing could be taken if the visibility allows.  However, in this example, there is also the option for a second aiming-off bearing to intercept the fence to the west of the summit.  We know that once the fence is reached, we just need to turn left and follow the fence to the summit.

An attack point can also be any clearly visible point close to the target destination which can be walked to directly without the need to aim-off.

Handrails

Handrails are linear features that can be used as a means of navigating and are especially useful in times of poor visibility.  Handrails can be paths, walls, fences, ditches, lines of fence posts, pylons, streams etc.  They can be used to take you to an attack point or directly to your target destination.

Many handrail features such as fences, walls, ditches, lines of old fence posts and are not shown on 1:50,000 maps. It is for this reason that the 1:25,000 maps are recommended for hill walking in the UK.

handrail

In the example shown two handrails are used.  The first is the trackway along which you walk until you reach the turn-off point.  The second is the fence line that runs from the trackway all the way to the summit.  In very poor visibility these handrails will take you directly to your target destination.

Slope Aspect

If you become lost on a hill or mountain in poor visibility the slope of the hill can provide important information about your location.  As long as you know which 1km grid square you are in, or what hill you are on, you just need to stand facing down slope.  Take a compass bearing of the direction of the slope and make a note of this.  This is the Slope Aspect.

Looking at the relevant square or hill on the map, move your compass around until you find a slope facing the same direction.  Draw a line on the map – you are somewhere on this line.  You know have two options.

slope aspect

Firstly, keep walking in the direction that you wish to travel, keeping a note of direction and distance.  Eventually you will come across a feature you recognise from the map or a change in slope.  This additional information could provide you with the solution you are looking for.

Secondly, if you are wished to get off the hill to a safe location, identify a safety bearing on the map, maybe to a road or river.  Set this bearing on the compass and, maintaining the same height, start to walk around the hill.  Check the down slope bearings as you go until it matches the bearing set on the compass.  At this point you are on your safety bearing and are now clear to descend to safety.

Contouring

One of the most important things to remember, when planning a route through a hilly or mountainous area, is that the direct route is not always the best route.  You may find that in the process of going from A to B you are going up hill, then downhill, only to go up hill again.  This uses up a lot of energy and may not be necessary.

A careful look at the contour lines might reveal that it is possible to go a longer way between A and B by following one contour line.  The distance may be greater, but the energy expended is greatly reduced.  This is called maintaining height or contouring.  It will also allow you to choose a more desirable route avoiding marshy valley bottoms or blustery ridges.

contouring finish

Alternatively, on a relatively level walk there may be one hill on the route.  Always consider the option of walking around the hill rather than over it.  Using Naismith’s Rule, calculate the time taken to go over the hill and the time taken to go around the hill.  If the go around is the quickest, then that is a ‘no brainer’.

Exercise:  Next time you are walking in a hilly area, practice walking around a hill or along the side of a ridge whilst maintain a constant height.  It is not an easy skill to develop, but it will come with practice.

Escape Bearings

A couple of years ago I made a classic school boy error and almost walked off a steep scarp slope in very poor visibility.  The reason for this is that despite having snow white out conditions, I did not use an escape bearing to leave the summit.  Regardless of weather conditions, you should always plan an escape bearing.

The purpose of an escape bearing is to get you off of the summit and back onto your descent route safely and avoiding all hazards.  Sometimes, you may need a more than one escape bearing depending on the circumstances.

Example:  When leaving the summit of Ben Nevis, the result of not using escape bearing could be the difference between life and death.  This is because of the proximity of very steep and deep gullies, especially to the north.  Starting from a known point – trip pillar – a bearing of 231 grid is taken for 150 metres.  At this point a grid bearing of 282 is taken until you reach the zig-zag footpath off the mountain.

nevis_bearing

Take every opportunity to practice all that has been discussed here.  Map reading and navigation is not just a case of learning, practicing once then assuming you are ready.  It takes constant practice to sharpen and maintain your skills.  Even now, after 50 years, I still practice my map reading and navigation skills on virtubally every walk I do.  Remember – practice make perfect.


In Map Reading & Navigation – Part 6, we will be covering night & bad weather navigation plus party discipline and organisation.

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