Dear Ann,

Your reader could probably increase the accuracy of using a map
wheel/string if she photographically enlarges the map (if she is allowed).
Or, if she enlarges the map she could probably also divide the rive course
into liner segments, and measure these using a conventional calipers+rule
(this is effectively what would be done if the map was a digital drawing.
The accuracy of the latter approach would depend on the numerber and
length of segments created.

But, I think the most important thing you reader has to do is decide
determine the precision she needs to measure to. Whatever method is used
be it digital or physical, it will be an approximation. So long as she is
consistent in her measuring then it should not be a mojor problem.

This is my ha'penny's worth.




On Fri, 04 Aug 2006 11:01:08 +0100, Anne Taylor <aemt2@...> 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
>



--
----------------------------------------------------------------------
Nicholas J. Verge BSc. FGS
Henley-on-Thames, Oxfordshire, UK

Geologist, amateur meteorologist & stormchaser
Member of European Storm Forecast Experiment (ESTOFEX)
http://www.estofex.org/