Re: Garmin Etrex Legend USA/UK
From: Chris Malcolm (cam_at_holyrood.ed.ac.uk)
Date: 02/01/05
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Date: Tue, 1 Feb 2005 10:16:30 +0000 (UTC)
"ah" <anonymous@discussions.microsoft.com> writes:
>"Chris Malcolm" <cam@holyrood.ed.ac.uk> wrote in message
>news:ctdrta$c8v$1@scotsman.ed.ac.uk...
>> You can *very* considerably reduce the number of points needed if you
>> omit those turning points where there is either no choice (you just
>> follow the path) or where the choice is obvious given the heading to
>> the next point. For example, if you were following a zig-zag route
>> through a lot of city blocks in a general diagonal direction you only
>> need one point, the destination, because each local zig and zag is
>> then an obvious choice of taking the turning which points you closest
>> to the destination heading.
>>
>> The mistake most people make in plotting GPS routes is to assume that
>> the route is going to be followed by a blind man, i.e., someone who
>> can only see the GPS screen and nothing else.
>I have no way of knowing if the choice will be obvious or not on the map,
>without going on site, because I do not walk in cities but in the
>countryside and sometimes the footpaths exist on the maps and are cut on the
>field. And I am planning on preparing my walks so that I am guided by the
>GPS, although I always have a map and compass when I hike.
The point is that you *do* have a way of knowing if the choice will be
obvious! The question is simply "is it wrong or right to make a
crudely obvious choice of direction based on which one is closer to
the heading to the next waypoint?" If the answer is "no" (or "don't
know"), then you need one or two local waypoints there to make the
answer obviously "yes".
If the track you're going to follow is either inaccurate or absent on
the map, then you need to be a bit of thinking about it, but no more
than you need to do anyway when devising a track or a route in such
case.
The method does work in making routes in trackless wild country. It
was to reduce the number of waypoints needed in following twisty
little tracks on hills that I first started using it. It stops the
actual route as displayed from conforming to the route you actually
walk, but the whole point is that once you get used to the idea that
it doesn't show you your tracks, but is instead a diagram which
generates direction choice information on the spot, that doesn't
matter.
-- Chris Malcolm cam@infirmatics.ed.ac.uk +44 (0)131 651 3445 DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/]
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