Call me Bob <
[email protected]> wrote:
> On Sun, 28 Jan 2007 13:15:08 +0000 (UTC), Chris Malcolm
> <[email protected]> wrote:
>>Check out http://gpsinformation.net/
>>
>>Lots of good advice and reviews.
> That does look good, I hadn't found it previously so thanks. Will have
> a read later.
>>Probably the two biggest questions to answer are whether you want a
>>mapping unit, which is more expensive, plus the downloadable detailed
>>maps are expensive in themselves. A non-mapping GPS, used an accessory
>>to paper maps or cheap free maps like google earth or streetmap, is
>>still very useful.
> My problem is that never having used a GPS before I can't be sure
> exactly which features I'm going to want and then use regularly, as
> opposed to what just sounds a good idea but then will be of little
> long term interest.
> I think I do want mapping capability.
> My main intended use is for the unit to guide me around pre-planned
> rides. I'd like to be able to plot a route at home, marking it up on
> the PC on my MemoryMap OS maps, upload it to the GPS, and then be able
> to follow the waypoints and arrows as I cycle along. I have a ****
> memory for directions and need to refer to a map frequently when
> riding in unfamiliar territory. That's a bit of a pain on my recumbent
> (my main leisure bike) because there's no easy way of mounting a map
> in front of me, so I'm forever digging about in pockets. I'm hoping a
> GPS will make this easier so I can enjoy my ride that bit more.
It will, but note that you don't need mapping capability for
that. Non-mappers allow you to download a route as a sequence of
waypoints, which you can then follow either with pointers to the next
waypoint, or as a display of your progress along the shape of the
route at any zoom level.
What a mapping unit gives you in addition is that you can see your
route superimposed on a map, showing roads, rivers, railways,
etc.. The level of detail you get in that map depends on how much
you've paid for, but it's never quite as much as you can get from an
OS paper map. It's more like the level of detail you get from a car
driver's road atlas map.
>>Finally note that for an extra cost you can add an autocailbrating
>>barometric altitude sensor to both mapping and non-mapping
>>models. That gives you much better accuracy of altitude, giving much
>>more accurate altitude tracks, profiles of hills climbed, and so
>>on. Some hill-climbing performance-measuring cyclists like that.
> I wouldn't describe myself as either a hill climber or a performance
> cyclist but a decent altimeter is attractive. I'd like to know about
> height gained and lost on my longer rides.
You'll get that from plain GPS altitude readings, but those at best
are 50% less accurate than GPS position readings, can be a lot worse,
and are rather noisy, i.e. jump up and down a lot due to random
errors. What the barometric altitude gives you is accuracy at least
twice as good, plus a lot less noise. But it's fiddlier to use, and
can give you really bad reading if you don't use it properly. It takes
a little bit of extra work on your part to get it to work properly,
and some people find that too much bother, and get very annoyed by the
consequent occasional misbehaviour.
> The Garmin models seem a popular choice. I understand if I want
> detailed mapping then I'll need to budget for some Garmin Mapsource or
> Topo software as the basemap might not be great, and my Memory Map
> stuff isn't compatible.
Your Memory Map stuff is incompatible in the sense of not being
downloadable as a detailed map display, but it is compatible in the
sense that you can use it to generate waypoints and routes of waypoint
lists which can be downloaded.
> At the moment I'm leaning towards the eTrex Vista Cx. It's one of
> their more expensive models, but it has mapping capability and the
> barometric altimeter, as well as a colour screen which I think may be
> useful for map display.
I think you may be able to check out what kind of detail you'll be
able to get from Garmin's web site. You might find it annoying if you
spend a lot of money on a mapping unit plus detailed downloadable
maps, and then find you have to carry paper maps anyway to get the
level of local detail you want. Car drivers often don't need that
detail, cyclists sometimes do, and hill walkers very often do.
For example, I use a lot of local cycle paths, and the required level
of detail is only available on special cycle path maps you can buy in
bike shops.
The general opinion seems to be that if you can afford it, go for as
much mapping as you can afford, because it's handy and nice to
have. But don't make the mistake the mistake of thinking, as many do,
that a non-mapping unit is somehow crippled and couldn't follow a
route or show you the shape of a track or where you are in relation to
a few nearby waypoints, and so on. Non-mapping units can do all of
that kind of thing, it's just that they do it as it were on blank
paper instead of superimposed on map detail. In effect non-mapping
units are plain paper mapping units in which the map you see consists
entirely of your own tracks, waypoints, routes, etc., no roads,
rivers, churches, etc..
A non-mapping unit is a very convenient and helpful accessory to paper
map navigation, sufficiently helpful that some people just use the
paper maps to plan their routes and decide on the waypoints. Waypoints
don't all have to be points you intend to go to, they can mark useful
visible landmarks for orientation purposes as well. So some people
with non-mapping units use their paper maps to plan their routes at
home, but when navigating the GPS alone is used and the map stays in the
backpack for emergencies.
--
Chris Malcolm
[email protected] DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[
http://www.dai.ed.ac.uk/homes/cam/]
