Navigation Strategies

Understanding The Nature of Navigation

Anyone thinking of heading out into the great outdoors should understand that there are three principal factors effecting navigation.

• Route Planning
• Route Following
• Route Checking

The potential for human error in navigation, can be high due to diminished concentration or distractions, therefore, route checking is an essential part of the process. This may occasionally, lead to re-planning the route while on the move to compensate for errors.

Navigation Strategies

Introduction: A first step in map reading or land navigation is to establish the coincidence between directions on the map and the corresponding directions on the ground.

Map Appreciation: Any map user must first become throughly acquainted with the style and layout of the map being used, and the information it contains before setting out. So it is advisable to study the map in order to develop a sound appreciation of the quality and quantity of information available. Also it should be possible for the map reader to generate and memorize a mental picture of the terrain which can be verified once out on the ground.

Orienteering or Setting the Map: Providing the map user has a good knowledge of his/her map position, setting the map by inspection is the simplest and quickest method. The procedure is as follows:

• Check your position on the ground and mark it on the map.
• Inspect the surrounding terrain for features that may be expected to be found on the map; select three well defined features.
• Identify the three features on the map then rotate the map so that the directions to the ground features coincide with the corresponding features as shown on the map.
• Check the direction to a fourth feature.

In areas of well defined detail, the procedure may be much simplified, so if you where standing at a cross roads or T junction all that would be required would be rotate the map so that the directions on the ground and on the map correspond.

In open hilly terrain it is necessary to identify relief (contour) features and to align the map with these.

In heavily forested areas the method of setting the map by inspection is unlikely to succeed and therefore some other method must be used. See example below

Setting the Map with a compass: If for any reason the map user is temporarily uncertain of his/her where about's, or if the terrain is heavily forested so that visibility is obscured, or if the map detail is very sparse, or if it is dark, the map must be set relative to north. For all but the roughest estimates of the direction of north, it is better and more reliable to use a compass to determine the direction of north.

Place the compass on the map, making sure that the north indicator is pointing to the top of the map. then rotate both the compass and the map together, once the magnetic needle matches up with the north point on the compass, that is the map set. See example below. Note click on the thumbnail

Map Orientation

 Image reproduced with permission of Ordnanace Survey and Ordnance Survey of Northern Ireland

Intersection

The most reliable method of fixing the position of a distant object or feature is by intersection. This method depends on observing the distant object or feature from at least two positions, and plotting the bearings to the object or feature on the map.

Where the two bearings cross each other on the map, this is the location of the object or feature.

Note: When taking the bearings from two different positions they must be at 150 metres apart. And remember to convert the magnetic bearing to a grid bearing.

Resection

You need to take three magnetic bearings of features or objects that you can see and locate on the map.

The three features or objects should be at least 120 degrees apart.

Repeat the procedure for a single back bearing for all three ( same procedure as for pinpointing your position). Once plotted on the map you should have all three lines forming a small triangle "what is known as a cocked hat".

Your approximate position will be within the triangle.

Staying on Course (Rule of Thumb)

A great technique that will help keep you from getting lost or confused.

• Fold the map so it is more managable.
• Find your location on the map.
• Hold your map in one hand with your thumb close behind your location.
• Move your thumb on the map as you progress along your route. When you come to an obvious feature on the ground move your thumb to mark your new location on the map.
• Keep your thumb on the map as a "You are here mark", doing this will save yourself time and confusion. 

Attack Point

To locate a difficult feature simply find another prominent feature nearby in this case a forest plantation. Once there follow the edge of the plantation to its corner and from that position use a combination of pacing and a new bearing to find your objective. (See above)

Aiming Off

Aiming off is when you deliberatly aim off to one side of your objective to miss it.

The reason you do this is, if your objective was on a linear feature such as a stream or path, say in this case a bridge over a stream. If you took a direct bearing to the bridge you may end up on either side of the bridge. Which way would you turn to gain the bridge in bad visibility or at night.

By aiming off slightly up stream, you will know when you get to the stream which way to turn.

Linear Features

Obvious linear features (besides paths) are field boundaries, edges of woods and forests, streams, rivers and lochs. other features can be ridges, spurs and valleys. This type of linear feature is called a handrail.

A handrail is simply a feature that is going in the direction you wish to travel, and you can follow it part of the way or completly to your destination. These types of features are a good aid to navigation.

Note:

Where possible the use of linear features should be used, however if you are intending to use a stream be very carefull especially in steep, rocky terrain, check the map. You may have to give the stream a wide berth due to gullies, waterfalls etc. This is more important in bad visibility or at night.

Collecting Feature

When you reach the point where your route or handrail changes direction, you must be aware that it is time for you to go your seperate ways. Some prominent feature located near this point is selected to provide warning.

This is called a collecting feature, it can also be used to warn you that you have gone to far.

Collecting Feature, Going to Far

In this example, you can see that we missed the turn in the path to take us up the spur. However we have come to the stream and this is acting has a collecting feature or a catching feature. This warns us that we have gone to far and need to re-trace our steps.

Moving around Obstacles

When travelling cross country it is not always possible to go in a straight line due to obstacles in your path. By using the method opposite along with pacing to go around features or obstacles will help you get back onto your original bearing.

Another way for example in this case you have a small lochan/lake on your bearing, on the other side you can see quite clearly a lone tree which on checking is directly on your bearing. Follow the shoreline around until you get to the lone tree, check bearing and continue.

The intervisibility example so far considered takes no account of the possibility of obstructions other than ground level itself as derived from the map. Heights shown on maps by spot heights and contours are heights of the ground surface. The map does not, in general, give the heights of buildings or vegetation and therefore it is essential that the map user should check the intended line of sight on the map for possible natural or artificial obstructions.

If after you arrive at an area, but cannot see your next checkpoint, this is often due to poor visibility. Refer back to your map and check for any features you can relate too. If this does not work you will need to do a systematic search of the general area. This is called a spiral search. See diagram opposite.

Spiral Search

This is a good method to use if you are on your own and have limited visibility. From your position, use your compass and walk North to the limit of your visibility and stop, using your compass turn 90 degrees to your right and walk twice the distance you did on the first leg, (pacing must be accurate). Stop again and turn right again 90 degrees and walk three times the distance this time, keep doing this extending each leg until you locate your chosen checkpoint.

Sweep Search

The only problem of the sweep search is that its nearly impossible to carry out if you are on your own. It's easily done if you are part of a group. Space the members of the group out evenly but within visual sight of each other. Sweep the area in extended line until you locate your check point.

Paths, Tracks and Water Features

Water Features:  Features such as rivers, streams and canals are usually shown by line symbols in blue.  seasonal streams are shown by blue pecked or dotted lines.  if rivers are wide enough, and the scale permits, they may br shown by double lines with blue infill; tidal rivers have outlines in black, those that are not tidal are in blue.

Locks, weirs, aqueducts and fords are shown as conventional signs or descriptions.

Lochs and other stretches of inland water are outlined in blue with a blue infilling.  Areas too small to be shown with a blue filling may be shown in solid blue.  Bogs and marshes are shown by a blue area and may be combined with green vegetation symbols.

All water features should be taken into consideration when planning a route cross country.

WHY?

• Weather: What has the weather been like the last few days, has there been heavy rain, if its been snowing, is there a thaw on, if so streams and rivers will be in spate.
• Safety:  If no suitable safe crossing place, ie, a bridge you will have to make a considerable detour  this will have a bounce on effect on your distance and timing.
• Remember: Do not under estimate the power of a stream or river when it's in spate, it is not just the force an volume of water rushing down stream, it's what you cannot see is the biggest danger, under the surface.
• Putting it simply never try and cross any water obstacle unless it is safe to do so.

Note:

• Thin blue line on the map indicates the width of water anything from 4 metres wide or less.
• Thicker blue line width from 4 metres to 8 metres wide.
• Water features with two darker blue lines with lighter shading in between 8 metres wide or more.

Picture below is of the River Nevis after one days heavy rain.

Tracks and Paths

Tracks, bridle paths and footpaths are usually shown by broken or dotted lines.

Thing to remember about paths is that the path indicated on the map may have not been used for some time, or the path could disappear quite suddenly and may be hard to find. Also paths will appear on your route that are not marked on the map, which one do you take, this is where your compass comes into use along with your map.

Path  The path shown below (left) is well marked on the map for its entire route, however it eventually disappears and is very hard to locate again.

Track: The track below (right) is part of the Kintyre Way, the section that runs from Tarbet to Skipness.  Well marked on the map and sign posted along its route.