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Maps for Walking, Hiking, Rambling, Running & Cycling

Blog archive

November 2 2018

November 2 2018

Altimeters
by Nigel Williams

An increasing number of devices carried in the hills have an altimeter mode. Maps are designed to replicate a 3D reality on a 2D surface. Contours probably account for a 3rd of the information we can get from a map, double that in winter, which is why they can be such a useful navigation tool. A compass similarly provides 2D information and an altimeter the 3rd dimension offering that extra 30% of information. Digital mapping however is reducing their use as a stand alone device.

There are two types of altimeter. The traditional barometric altimeter which measures air pressure, and the GPS satellite based system. Some GPS devices have both systems. GPS readings can be inaccurate close under cliffs or on steep ground. Barometric altimeters can be inaccurate on ridges and cols where the wind creates a vortex or is funneled, creating pockets of low and high pressure. Both rely on battery power for a digital reading, although traditional barometric altimeters are analogue.

The higher we go the less the air pressure. This is how the barometric altimeter works. However, the device needs to be calibrated at regular intervals.

A synoptic weather chart uses isobar lines similar to contours. These are lines of equal pressure. A typical Low pressure series of concentric circles crossing the Atlantic and passing over the UK travels at about 25mph regardless of the wind speed. Those lines would pass overhead if we stayed in the same place on the ground. As the centre of the Low comes towards us the pressure decreases giving a higher altitude reading. As the centre of the Low moves away the pressure rises giving a lower reading. 3 Isobars passing over will change an altitude reading by about 100m. Therefore a manual adjustment is required every 30 or so minutes at known heights on the map. The car park, path junction, hill top etc. It also means that they are not super accurate but will be within 10 metres or so.

On multi day journeys barometric altimeters provide a weather forecasting tool. When waking in the morning, if you find that the altimeter suggests you have slid downhill 100m you know the weather is improving - high pressure is developing. If you have been elevated then low pressure, probably poor weather is on the way.

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November 1 2018

November 1 2018

It's Getting Dark!
by Nigel Williams

As the nights close in rescue teams are being called out to search for people in difficulty. Often this is a confidence as much as a navigation issue.

Preparation is key before it gets dark. Walking poles are helpful across difficult ground at night, but they can be a distraction from using the tools of navigation which need full concentration. With reduced vision other senses can kick in. Contours, feeling the ground and listening for running water can be key to navigation.

Prior to darkness, stop, have a snack break and make sure navigation tools are easily accessible. Moving at night can be slow and the temperature may drop. Keep hats, gloves etc. handy and put the head torch on your head (switched off). If need be, call friends to let them know you are running late. There is often a better signal on the tops. Set the first or a key bearing on your compass. If using the phone gps function to back up map and compass, turn to airplane mode to extend battery life and try to use it just for checking your position.

Study the route in detail and plan to follow linear features such as paths, streams, fences and ridges all the way, even on a longer route. Whilst following linear features don’t ignore the third dimension. Note the angle you expect to cross the contour lines and changes in contour spacing identifying steepening and shallowing of the slope. Recognise other features along the route such as stream crossings. These all provide non visual tick off features. Keep a rough check on the direction of travel with the compass needle. If a star on the horizon aligns with the route it can be used for 20 -30 minutes but they all move except the North Star.

Try to keep the torch off for as long as possible. Night vision will develop as it gets dark. Head torch beams tend to focus our vision. Turning off all lights, wait a few minutes for night vision to develop then squat down to silhouette the landscape around for an improved view of the terrain.

Lastly, to help keep an element of night vision, close one eye when there is a group discussion around the map and headtorches are dazzling.

Night navigation is not difficult but does need concentration and a bit of confidence.

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October 2018

October 2018

The psychology of getting lost
by Nigel Williams

Being lost, "temporarily geographically embarrassed" or "cartographically challenged" happens to all of us at some time in the outdoors. It is only a temporary state but can be stressful, frustrating and even embarrassing.

Most people have vivid memories of being lost. They can recall the situation in remarkable detail because of the fear and stress of the situation. But why should it create these emotions? It may go back to the Stone Age when there were real threats out in the woods. However, common modern day experiences may also have a part to play.

Ask any group to recall the very first time they had a frightening experience of feeling lost. In a supermarket as a toddler and separated from a parent is a common response.

So first we have a state of high anxiety and a feeling of isolation and the unknown. There are a number of common responses to the situation at that age. Standing crying is the most common, but “fright and flight” can kick in sending adrenaline to the legs resulting in a frantic running around the aisles (more likely to be the parent).

When found we may witness facial cues and expressions of relief, even tears, the like of which we have not seen on the parent before, making us subconsciously aware that this has been a big event. (Decades on people often remember detail such as the dress their mother was wearing.) Lastly we often get a serious telling off just to compound the awfulness of the whole episode. Then for the next decade of our lives we are exposed to fairy tales about being lost in the woods.

It seems hardly surprising that all this sets off high levels of anxiety and emotion which interferes with rational thought and actions. It is embedded in us at an early age. Unfortunately in the outdoors it may be backed up with limited or unpracticed navigation skills.

In reality we are usually misplaced rather than lost. We generally know we are somewhere on the map and not in genuine danger. Getting lost might result in being late or a long walk back to the car but the only harm done is usually to our ego.

From personal experience though, getting lost seems to help practice the skills and diminish the anxiety, unless you are leading a group!

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