Garmin Nuvi - poor routing decisions?

ifconfig

I've had a Garmin Nuvi 360 since this time last year.

It was of good assistance when we were in Brittany on holidays last July/Aug. It has however, let us down when on trips within rural/tourist trails in Ireland.

For example - on Saturday we took a journey from near Delphi adventure centre in Connemara and we were on the R335 at Cregganbaun.
I got it to plan a journey form Cregganbaun to Westport, Co Mayo.

It tried to route us to make a right/eastward turn at Tully rather than the logical route which Google maps directions correctly calculates which is to continue northbound to Louisburgh on the R335 and then on to Westport via Lecanvey.

When I got home I simulated the same route using the Garmin and even with any combo of shortest time, car , shortest distance, bus, truck, avoidances added in or out it persisted to always force the route to take
that tertiary (if not lower) route of going via Tully !?!

Why doesn't the unit provide a setting which locks the route to national approved roads ? ..or.. am I missing something here ?
We had the same about 8 months ago when going to Belfast via Blacklion (Cavan/Fermanagh). I can't recall the exact deviation it took but it
appeared to wish to route us down a very obscure rat run for want of a better phrase. The only way I can see I can force it not to is by identifying a route point which prevents it from straying on to these eccentric routing decisions.

Anyone care to explain ?

ps - here is the Google maps routing which I wish the Garmin provided:
fill this in on google maps:
from: cregganbaun ireland to: westport mayo ireland

--ifc

Alun

The problem with most satnavs is that they base their routing decisions (when in 'fastest' mode) purely on the speed rating of the road in question (as supplied by Navteq), not on any subjective idea of their importance, so it's quite common, for example, to be taken off a pretty decent R road to cut a corner off on some obscure boreen if it'll save (according to the distance travelled) even the tiniest amount of time .. both roads will have an 80km/h rating. In fact I don't even think the Navteq data goes that far, they have sped categories, that don't necessarily tie up with all the different countries national speed limits.

Maybe Google have added some smarts to their routing algorithm, that 'knows' about 'M', 'N' and 'R' roads, I don't know.

ifconfig

Alun wrote: »

The problem with most satnavs is that they base their routing decisions (when in 'fastest' mode) purely on the speed rating of the road in question (as supplied by Navteq), not on any subjective idea of their importance, so it's quite common, for example, to be taken off a pretty decent R road to cut a corner off on some obscure boreen if it'll save (according to the distance travelled) even the tiniest amount of time .. both roads will have an 80km/h rating. In fact I don't even think the Navteq data goes that far, they have sped categories, that don't necessarily tie up with all the different countries national speed limits.

Maybe Google have added some smarts to their routing algorithm, that 'knows' about 'M', 'N' and 'R' roads, I don't know.

Thanks Alun.
That was my hunch as well. Although - I'm pretty sure I tried both fastest time and shortest distance and I even posed as a bus or truck and it still tried to divert me that way. I must take a look at the actual full route it was proposing. Looking at the Google map it was pointless straying us off the main 'R' route since the it was more or less leading us into a warren of extremely minor roads perhaps in order to bring is very far eastwards towards the N59.

How much, btw , might I be looking at to get the maps updated to 2010 navteq/Europe ? Mind you - I know it's not the maps which are the issue but the routing algorithms.

-ifc

Alun

ifconfig wrote: »

How much, btw , might I be looking at to get the maps updated to 2010 navteq/Europe ? Mind you - I know it's not the maps which are the issue but the routing algorithms.

You can either do a one-off update or a quarterly life time update, and there's very little price difference between the two. £79.99 for a one off and £99.99 for the lifetime one, so if you're going to update more than once, it's a no brainer.

http://www.garmin.com/garmin/cms/site/uk/lang/en/numaps

Alun

ifconfig wrote: »

Looking at the Google map it was pointless straying us off the main 'R' route since the it was more or less leading us into a warren of extremely minor roads perhaps in order to bring is very far eastwards towards the N59.

I just had a play with Google maps and dragged the route off on to that minor road at Tully and it saves just over 2 kilometres, so there's your answer! It thinks that you can actually do the same speed over that road as on the better R road. Until Navteq actually introduce some kind of real life assessment of a road's qualities you're stuck with that kind of thing, I'm afraid.

One point worth making is that Google uses Teleatlas mapping, and it's quite possible that they have their speed categories better sorted than Navteq do. Maybe someone with a TomTom can chirp in here and simulate that route on their satnav to see if it's just a map issue, or some Google cleverness that accounts for the differences.

ifconfig

Thanks for all the help Alun.

Yes - it does appear that the Garmin's might tend to overestimate speeds
on tertiary/quaternary roads as in this case.

Thanks also for the link on the Map updates. The lifetime option looks good. The Garmin comes into it's own when finding the correct exit on a motorway or dual carriageway say in France, etc. I find that a map is a lot more useful when doing weekend driving in Ireland. To be honest my wife has never
trusted it for Irish journeys

-ifc

**Timbuk2**

I know exactly what you are talking about! Sometimes the Garmin Nuvi can be just dreadful. It has often tried to route me up roads that were only a car width. It even tried to route me onto a road with a large amount of grass in the middle, just to put me back onto the road I left at a further up point.

For example:
Leaving Carrick-on-Suir in the Dungarvan direction, it tried to route me on a small road by the golf course which would lead me back onto the road, avoiding the hairpin bend as it climbs the hill (not a bad hairpin bend either)
At Lyracrumpán (sp?) in Kerry, it routed me onto possibly the worst road I've ever seen in my life. Big strip of grass in the middle. I quickly turned back off it ("Recalculating..")

There should be an option to only use roads that have lines in the middle :rolleyes:

I agree, the Google Maps is top notch (9 times out of 10) in forming routes. And I find the Google Maps is generally up to date with new-ish roads. There's nothing worse than driving on a road and to hear "Recalculating" out of nowhere as the satnav thinks you have sidestepped onto another road, where in fact the road has been rerouted or a bypass has been built. I usually just turn it off because the road isn't on the map so it recalculates every minute. An example is the M8 north of Cashel

parsi

**Timbuk2** wrote: »

Big strip of grass in the middle. I quickly turned back off it ("Recalculating..")

There should be an option to only use roads that have white lines in the middle

Fixed that for you

peking97

**Timbuk2** wrote: »

I know exactly what you are talking about! Sometimes the Garmin Nuvi can be just dreadful. It has often tried to route me up roads that were only a car width. It even tried to route me onto a road with a large amount of grass in the middle, just to put me back onto the road I left at a further up point.

For example:
Leaving Carrick-on-Suir in the Dungarvan direction, it tried to route me on a small road by the golf course which would lead me back onto the road, avoiding the hairpin bend as it climbs the hill (not a bad hairpin bend either)
At Lyracrumpán (sp?) in Kerry, it routed me onto possibly the worst road I've ever seen in my life. Big strip of grass in the middle. I quickly turned back off it ("Recalculating..")

There should be an option to only use roads that have lines in the middle :rolleyes:

Did you have *Unpaved Roads* ticked under *Avoidances*?