27 December 2010

Timing (For Mountain Skills)

Timing is a technique used for Mountain Skills/Mountain Navigation, especially over distances of more than 500 metres, or over steep, broken ground. It's mainly used in bad visibility or for night navigation.

Timing is measuring the distance you will be walking between two points, then calculating how long it will take to walk that distance.

You need a 1:50 000 OSI Map, Silva Type 4 Compass and Stop Watch.

Stage 1
1. Break your journey into short, manageable legs, for example, from a spot height to a saddle.

2. Measure your map leg distance, using the millimetre ruler of your compass.

3. 1 millimetre = 50 metres
If you measure 18 millimetres, between your spot height and your saddle, then the distance is 900 metres.

4. Naismith's Rule: Average Hill Walking Speed - 5km per hour
This Breaks Down As:
5km per hour
1km per 12 mins
500 metres per 6 mins
100 metres per 1 min + 12 seconds (call it just over 1 min)

5. So if your distance is 900 metres, use the above table to calculate the time it will take to walk:
900 metres = 10 mins + 48 seconds (call it 11 mins)

Stage 2
You now have your main timing figure of 11 mins, which is how long it will take to walk 900 metres; however you need to allow for any uphill climbing, which is going to slow you down.

1. Count how many uphill contours you cross and for each uphill contour you cross, add on 1 extra min. So if you cross 8 uphill contours, add 8 extra mins to your original time.
11 mins + 8 extra mins for uphill contours = 19 mins total

Stage 3
Ignore downhill contours; only allow for uphill contours.

Stage 4
You now know it will take you 19 mins to walk from your spot height to your saddle.

1. Start your stop watch once you begin walking and if you stop to check your map make sure you stop, then re-start, your stop watch each time. Don't forget this!

2. As you approach 19 mins you want to be carefully looking out for your destination point, as you should allow a couple of mins margin on either side of your calculated time.

3. You should be at your destination after 19 mins. If not ask yourself if you may have overshot it.

4. If you haven't overshot it, walk on for an extra 5 mins only and you should have arrived at your destination.

Timing is a great technique, used in conjunction with other Mountain Skills techniques, to navigate with.

It can be an excellent Cut Off Point, which tells you that you should walk no more than, for example, 19 mins, plus an extra 5 mins if necessary, to reach your destination point.

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