Author Topic: A slope-measuring tool  (Read 2192 times)

captain paranoia

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A slope-measuring tool
« on: July 11, 2012, 01:09:02 PM »
Having been reading up on 'formal navigation techniques', having started helping with DofE, I discovered the 'Keayscale' in Wally Keay's DofE Navigation book.  This has scales along the side of the tool that allow you to measure the gradient of a slope by comparing the contour spacing with fixed gaps.  The gap represents a number of contour lines.

As usual, this started me thinking about how I might do it better, and I thought I'd probably draw the contour lines within the gap, rather than simply write on how many lines there should be in the gap.

This then lead on to the thought of using a continuous scale, rather than discrete values.  A bit of simple trigonometry and some PostScript programming later, and I have a script to generate a slope-measuring tool for any map you can think of.  Here's an example (a rather low resolution version):



The tool should be printed onto a transparency, and used by sliding the tool across the amp at the area of interest until you find the point at which the tool and map contours are the same; then you read off the slope.

The script allows the user to enter the parameters for the map in question, and the tool:

map series title
map scale
map vertical contour spacing
map vertical scale factor (for non-metric maps)
map vertical contour units
number of contours between 'index' (thicker) contour
number of index 'series' to show on the tool
minimum slope angle
maximum slope angle
values to display on the axes
physical size of the tool

It will accept a whole series of these map definitions, and print them on a transparency.

Having done all this, and made a few tools, I'm not entirely sure that the tool is that necessary, as it doesn't really tell me anything about the slope than I can already tell just by looking at it.  But other people have made slope-measuring tools, and I thought I'd have a go...  Someone has suggested that a narrow-range tool could be used to identify avalanche-prone slopes.

I have a version which will show the additional 'along slope' distance, too, but, again, I'm not convinced that that's a useful technique; by the time the slope is steep enough to make a significant difference to the distance, the slope is steep enough to change my stride, and slow me down, which will have a much greater effect on pace-counting or timing than the small difference in distance...

I'm also not entirely convinced by the continuous curve, and may go back to a discrete, stepped curve, as it may be easier to use.

If anyone is vaguely interested, send me an email address, and I'll send the PostScript file.  Or, if you're not sure about handling PS, I'll send a PDF, but that loses the ability for the user to specify their map details. [discovers attachment option: PostScript attached]

Comments and suggestions are welcome.