• Ash

Navigation Puzzle 7

Last week we looked at Naismith's rule.


This is a good, but very rough measure of how long it will take to move along a certain route.


In 1892 A Scottish mountaineer, Philip Tranter, offered the Tranter's corrections to Naismiths rule.


With this, he suggested a table of adjustments. It is based on the time taken for an individual to be able to cover 800m (half a mile) of distance with an ascent of 300m (1000 feet).


Then by adopting Naismith's time you apply these:

So, if you know you can cover the 800 m and 300m of ascent in 15 minutes, then you'd be using the top row in black.


So if Naismith calculates an 8 hr walk, then with Tranter's corrections it would five and a half hours.


However, if you take 30 minutes to cover the same 800:300m route, then the same 8hr walk would take you twelve and a half hours.


Then in 1984 Langmuir suggested that descent times should also be adjusted, so taken that into consideration the suggestion is that we subtract 10 minutes per 300 m descent for slopes between 5 and 12 degrees (roughly 1:11 - 1:5. At 1:5 for every 100m forward we descend 20m or for a tenth of the kilometrebox we cross 2 10m contour intervals) ; and add 10 minutes per 300m descent for slopes greater than 12 degrees.


This week's task is to calculate the times for this walk - the GPX for it is here - it may be helpful to add it to digital mapping software to look at it for Langmuirs corrections.

The overall distance is 14.5km and has a total height gain of 705m.


For Tranter's corrections, assume you can cover the 800m with 300m of ascent in 14 minutes.


Applying Langmuir takes a bit of observation on the map. But to be super helpful, the GPX file can be put through GPS visualiser and then, but setting the max colour limit to -5, only descent slopes of greater than 5 degrees are coloured in. So, the profile looks like this -


Three answers needed this week, from one route. Shouldn't take you too long - haven't a formula for that though! ;-)


Do you want the answers on Friday - let me know with a comment beneath!






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