On 08/11/2010 12:55, chris French wrote:

snip

Garmin was helpful and competent.

I have likewise had excellent help from Garmin for a hand held GPS.
For that reason (and the fact that the Garmin was the only equipment
to take grid references) I bought a Garmin sat-nav for my car.
Unfortunately the route finding abilities of the Garmin left much to
be desired - the basic problem being that it was wildly over
optimistic (by a factor of two or more) about what was possible on
single track roads leading to endless 'short cuts' that took
considerably longer than sticking to classified roads would have. The
timing of the directions also left much to be desired.

We have a cheapy Myguide Satnav, it seems to also like doing this,
though I imagine they all do it to a certain extent, depending on the
weighting given. It also seems rather pessimistic on Motorways.

It is some time since I switched but my memory of the Garmins (the hand
held had a rudimentary road map and much the same routing software as
its car borne cousin) was that the average speeds on major roads were on
the high side but, unlike those for single track roads, achievable in
light traffic. I formed the distinct impression that Garmin didn't
really care whether the road was a single carriageway or a single track,
it still got an average speed circa 40 mph. TomTom by contrast claim
their average speeds are based on real drivers. I don't hang about and I
now find that I get a cushion in the ETA which covers all but the worst
of unexpected traffic jams.

I don't know if fancier ones allow it, but some way of tweaking the the
way it chooses the roads would be useful. And a way to learn over time
how long you take over certain types of roads.

Both the Garmin and the TomTom allow you to chose fastest or shortest
and I think to avoid Motorways but Garmin's shortcoming is the values it
gives to individual lengths of road. Fastest can't be worked out without
having both time and distance in the equation.

I eventually junked the Garmin and bought a TomTom which is much
better in almost every aspect. However it, like the Garmin before it,
has thousands of junctions coded with the wrong priority and also one
or very odd quirks such as advising keeping right to avoid driving
into a bog standard roadside lay-by on the A66.

Ditto, doesn't all the mapping for these things come from a couple of
companies (Navteq and someone else?), so I guess the same problems will
occur with multiple manufacturers.

Probably. It is a feature I find irritating rather than misleading under
most circumstances but again Garmin falls short of TomTom in not
displaying as many minor side roads along the way and sometimes even a
prolonged look at the display (not to be recommended while moving)
leaves the next turn uncertain.