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The Garmin backroad problem... how bad is it really?
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daysleeper
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Joined: Dec 03, 2007
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PostPosted: Mon Dec 03, 2007 8:19 pm    Post subject: The Garmin backroad problem... how bad is it really? Reply with quote

I'm trying to choose between a TT and Garmin satnav. Thing is I've been reading on here and various other sites about the routing issue where Garmin stuff seems unable to tell the difference between a normal A road (60MPH) and a farm lane (10mph) as both have the same speed limit, technically.

As I live in Devon and spend a fair amount of time in places where the shortest route often takes way longer than driving 3 sides of a square on better roads it has me a little worried. Confused

Anyone tell me just how bad this issue really is or is it being over exaggerated?
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Skippy
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PostPosted: Mon Dec 03, 2007 9:35 pm    Post subject: Reply with quote

Welcome

It probably doesn't happen that often but when it does, it can produce some real howlers. If you can give us a few examples then I can test out the routing and tell you which way it would go.

I did Padstow to Newquay once and it took me though High Lanes, Rumford, St Eval, St Mawgan and then down the coast road into Newquay. Some friends in another car were using a map and they got straight on the A39 and arrived quite a bit sooner than me!

This happened using the v5 maps, I have the version 9 maps now and it still calculates the same route. Version 10 maps are out soon, but I think the problem is in the routing algorithm not the maps themselves. The worst thing is that Garmin know about the problem but they won't fix it.

I really like Garmin units, but if you live in a rural area then I would seriously recommend that you consider getting a TomTom...
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swing
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PostPosted: Mon Dec 03, 2007 9:46 pm    Post subject: Reply with quote

Of course, if you know the area, you'll know that the 3 sides is faster, and you'll drive that way, irrespective of what the SatNav says.

I've often (maybe 5 or so times this whole year) been directed down what turned out to be tracks, but each time my Garmin has directed me that way I was actually able to guess it was going to happen well before the road got narrow, and decided to accept the inevitable, instead of heading back to a more major road, so yes, it happens if you let it, but it's always (for me) been a valid route, albeit a narrow route.
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mikealder
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PostPosted: Tue Dec 04, 2007 12:16 am    Post subject: Reply with quote

This problem is down to how the roads are classified a national speed limit can apply to a duel carriageway as well as a back lane with limitted access, the Garmin will use the same data for either road and calculate based upon distance, this was confirmed to us at the NEC Outdoors Show when we asked the question about the issue earlier this year (Alix776 probably has more details as he's asked the question).

At the end of the day you are in charge of the vehicle and if the road looks unsuitable don't use it, the nav unit will soon find another route, only once have I been thrown off road down a real dirt track using sat nav technology, it wasn't Garmin or TomTom in fact being PDA development beta test software that has now been fixed this isn't an issue even with this package.

It is down to Garmin to sort the map data out and the way in which roads are classified, I hope the impending new maps can resolve this though as it is a weak point IMHO - Mike
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Skippy
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PostPosted: Tue Dec 04, 2007 12:29 am    Post subject: Reply with quote

mikealder wrote:
At the end of the day you are in charge of the vehicle and if the road looks unsuitable don't use it


It's not always immediately obvious that the Garmin is going to send you down the lanes until it's too late. It often happens that you are sent down a series of roads which get more and more narrow or the road narrows as you climb a series of steep hills.

mikealder wrote:
It is down to Garmin to sort the map data out and the way in which roads are classified, I hope the impending new maps can resolve this though as it is a weak point IMHO - Mike


I don't think it's the map data which is at fault, it's the way Garmin uses it. If you look at the roads in Mapsource or on the GPS unit then it is quite plain that these are unclassified roads, yet still it routes down them. Mad
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mikealder
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PostPosted: Tue Dec 04, 2007 12:43 am    Post subject: Reply with quote

I only use my Gamin for camera verification as I don't like the HMI or trust the routing but for what I need from the device it is brilliant, the map data issue could be the Garmin device sofware but that is easy to fix with a new release, the map data containing the error is more fundamental, whilst NavTeq supply the data do Garmin strip it out in order to reduce memory card requirements in which case the end user sees nothing in way of a difference between back country lanes and the A roads carrying the national speed limit - Mike
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crazyfingers
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PostPosted: Tue Dec 04, 2007 2:52 am    Post subject: Reply with quote

I don't have any such problem with my Garmin iQue. Of course one needs to set the preferences to take the fastest route, not the shortest.

If anything, my iQue prefers the highways too much.

In a few weeks I'll bee able to tell if the Nuvi (750) behaves differently.

All North America versions.
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daysleeper
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PostPosted: Tue Dec 04, 2007 8:29 am    Post subject: Reply with quote

Hmm, you'd think it would be a fairly simple coding fix....make all unclassified roads speed = 20mph. Then you'd still use them in shortest but not in fastest.

I dunno, the forums are full of people having grief with TomTom and this seems to be the only complaint with Garmin, but its a fairly fundamental one.
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Skippy
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PostPosted: Tue Dec 04, 2007 12:13 pm    Post subject: Reply with quote

mikealder wrote:
the end user sees nothing in way of a difference between back country lanes and the A roads carrying the national speed limit


They do actually. Garmin maps are arranged in layers so it knows which roads to display at each zoom level. The lowest layer shows all the unclassified and residential roads so the Garmin does know that these are minor roads.

As daysleeper says - they could just mark all these lowest layer roads as 20 MPH for route calculation purposes and the problem would disappear. I think the worry is that messing about with the routing engine could potentially cause a lot of very strange routes and no one at Garmin is willing to grasp the nettle on this one.
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Lester_Burnham
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PostPosted: Tue Dec 04, 2007 12:31 pm    Post subject: Reply with quote

mikealder wrote:
It is down to Garmin to sort the map data out and the way in which roads are classified, I hope the impending new maps can resolve this though as it is a weak point IMHO - Mike


My understanding was that there was nothing wrong with the map data, per se.

I understood the issue to be that Garmin (and perhaps others) had changed their routing algorithms so that merely the speed rating of the road is used, as opposed to factoring in other aspects from the map data (ie class of road - which is surely in there, because of how the roads are drawn on the screen).
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missing_user



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PostPosted: Tue Dec 04, 2007 1:03 pm    Post subject: Reply with quote

NavTech draw the Maps.
Garmin provide the software and the units.
The end result is not always what we expect in the UK, as their interpretion of roads is not the same as ours!!

After 5 years of Garmin use I offer:-

1-Set your unit to the 'truck' option [it gets out of the possibility of 'unpaved roads'.

2-Never rely on the 'unit' routes - always plan them on the PC with Mapsource and transfer them.

3-Never buy a unit without the PC facility.[a MapSource DVD not pre-loaded SD]

4-Never buy a unit without the option to place several vias.

5-Never buy a unit that does not save and store your routes.


I am a member of the most hated group of drivers [caravanners] and I have never had the experience of getting lost down country lanes.
I planned my recent caravan holiday to Rome, Venice and Sorrento [4200 mile round trip] on the PC and stored each day's route within the units, weeks before going!

Try:-
With a Garmin unit or on MapSource, two different options for a common route, taken by many European motorists.

Rosslare/Fishguard Ferry to Dover/Calais ferry.
The settings - 'car' will take you on a scenic tour in Pembrokeshire.
The setting - 'truck' will take the obvious route through Pembrokeshire.
I reported this problem to NavTech and Garmin - Garmin ignored it - Navtech gave me a detailed answer/reason-Garmin interperate the road details incorrectly.
CityNavigator will always take you through Basingstoke so you need a via at M4 J4b in both directions!

Too many motorist buy a GPS unit - turn it on - and turn their brain off!
The units are to be used as an 'aid' to navigation Very Happy
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inspiredron
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Joined: Dec 17, 2006
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Location: Ellesmere UK

PostPosted: Tue Dec 04, 2007 5:48 pm    Post subject: Reply with quote

The Garmin map engine is weird sometimes.

1. Recently the fastest route took me off a main road and round 3 sides of a small square to rejoin the same main road half a mile later. There was no adverse traffic report to need this diversion. This is a common route and it's the first time it has made this diversion.

2. Some time ago I reported to NAVTECH that the mapping data was wrong at a specific location and that, when travelling South, my Garmin directed me around the roundabout ANTI-clockwise. Their response was:
"Our Resolution Outcome is: No Change Necessary - Database Reflects Reality
Details: Based on database verification, it was found that the roundabout on the A217 (at its junction with Chipstead Lane) is correctly represented in the NAVEQ datbase with the one ways directed in a clockwise direction. As a result, no changes have been made at this time.

Try it on your Garmin in simulation mode! The location is on the A217 about 3 miles N of M25 J8. I have had the same results on a C510 and a Nuvi 660.
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missing_user



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PostPosted: Tue Dec 04, 2007 7:42 pm    Post subject: Reply with quote

Fantastic result!
I tried it and it was anticlockwise!
Not as serious as taking scenic route off the Fishguard Ferry with a caravan!! Very Happy
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inspiredron
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Location: Ellesmere UK

PostPosted: Wed Dec 05, 2007 12:24 am    Post subject: Reply with quote

strumble wrote:

Not as serious as taking scenic route off the Fishguard Ferry with a caravan!! Very Happy


MORE serious if you use the Garmin blindly! Very Happy
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Eagle15
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Joined: Aug 30, 2007
Posts: 26

PostPosted: Wed Dec 05, 2007 7:48 am    Post subject: Reply with quote

I use my Nuvi for my job which is driving 7.5 tonne lorries. It is set to 'Lorry' and 'Fastest Route'. About once a week it tries to send me down a single track road (different ones in the Midlands). Yesterday it sent me down a single track road that turned into an unpaved farm track. It can be fun trying to turn a 7.5 tonne lorry round on a single track road.
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