Ann, I think it should be noted that 'lengths' of natural phenomena
are scale dependent and there is no such thing as 'true measure'
independent of scale. Fractal geometry comes in here, I believe, but
the phenomenon can be easily seen by imagining a series of
enlargements as you zoom in from above. The closer you get, the more
convoluted (& longer) the edge being measured and this continues into
the microscopic level.

iain taylor
Halifax, NS

At 11:01 AM +0100 8/4/06, Anne Taylor wrote:
>Dear all
>
>A reader (who is doing an 'A' level project) has asked our advice on the
>best way to measure stream/river length on 1:10,560 or 1:10,000 scale maps.
>The project is on river sinuosity so the measurements have to be fairly
>accurate.
>
>We have suggested a map measurer (the rather old one we had slipped too
>much); the cotton/string approach; marking the sections of the river along
>the edge of a piece of paper.
>
>None of these was thought to be overly satisfactory.
>
>She has seen adverts for the 'MapWheel' - details at
> http://scalex.com/pdf's/MapWheel%20Flyer.pdf Before she spends GBP
>20-plus on one I said I would ask if anyone has experience of using one and
>might comment (off-list if you prefer) on its accuracy.
>
>Any other suggestions gratefully received. She does not have access to GIS
>
>Thank you
>
>Anne
>
>
>Anne Taylor
>Head of Map Department, Cambridge University Library, West Road, Cambridge
>CB3 9DR
>Tel: 01223-333041. Fax: 01223-333160. email: aemt2@...
>http://www.lib.cam.ac.uk/maps/Home.htm
>
>
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