Thread: In Car GPS

a quick check on a larger screen makes any error pretty clear

I disagree. Yes, in that particular case, it might stand out like dog bollocks but I'm willing to bet that there are hundreds if not thousands of cases where what appears on a flat map to be the straightest, most direct route, is in fact the slowest. You must at least concede that - surely the Merimbula to Sydney route proves it. And if you do concede that, you must also concede that if you don't know the road, then you wont be able to determine that just by looking at the shape of the route. You would need to know the local conditions all along each route. So given that, on what other basis can you possibly select a better route? Further, if you know the road well enough to be able to select the best route yourself, why do you need a GPS?

And once again, let me point out that I am not criticising you for wanting to manually check the route yourself, which is fine by me. I am disputing your assertion from page two that putting blind faith, as you put it, in the calculated route is the incorrect way to use these devices. I believe that is exactly what you are expected to do, otherwise the technology is pointless.

Originally Posted by silentC

I asked Tom Tom for a route to Sydney CBD and it goes via Canberra, which is 6:00 hours - 522km. Calculate alternative gives the coast at 6:19 hours - 454km.

The coastal route is showing 452km and 5hours 19 minutes 40 seconds.

The Canberra route shows 526km and 5hours 46 minutes 13 seconds.

At this point I think I would be losing trust in both units and investigating further.

I know from 20 years experience that the Hume route is quicker if you are going into town, to the western suburbs or to the northern suburbs. If you are going to the south, the coast road is quicker and Tom Tom confirms it.

So far on the routes I have travelled that I have good knowledge of, it has been on the money. I have no reason to believe it will do a worse job than I would on the routes I don't know.

Silent, I think there is enough discussion here from both sides for readers to decide whether to use blind faith or maybe to check it over for themselves on longer trips. Clearly each of us won't be swayed from our positions.

Can I ask a question here?

I used to travel to Perth every 2 months for a week on business. Now at that stage Perth had a funny one way system of streets/raods around the CBD, in the morning they would go one way , in the afternoon they would go in the opposite way. Very interesting for a first time visitor, I tried to go back to my hotel in Hay Street the same way I left in the morning, but didn't know about this interesting local phenomenon.

My question is, how would a GPS cope with this, assuming the system is till in place.

Do these GPS units know about one way streets, in particular one way streets that change direction?

Adelaide has one of these as well, the Southern "Express" Way, only in to the city in the morning, only out of the city in the afternoon.

So how do the GPS units cope?

whether to use blind faith or maybe to check it over for themselves

Let's rephrase that to:

"whether we should put our faith in the technology in lieu of personal experience of the route or be distrustful of the technology despite the lack of personal experience of the route".

Yep, that sounds better. "Blind faith" implies ignorance or foolishness and I'm sorry but I cannot accept that. I will in return restrain myself from using the term 'luddite'

I can test your GPS systems for you - free ! Your location is Hastings St Noosa heads QLD - your destination is Lanyana way , Noosa Heads - I would be very curious to know what route the GPS systems tell ppl to go.

Thanks guys. Just bought a Tomtom one V3 for the directionally challanged wife.
I don't think I will need to check her routes as she will be within Canberra only.

Looks like I should check any major trips just incase.

But whoever blindly trusts a computer is going to end up in the wrong place. A few checks are easy and will not go astray.


ps some people need to get back to wood work.

Originally Posted by Dirty Doogie

I can test your GPS systems for you - free ! Your location is Hastings St Noosa heads QLD - your destination is Lanyana way , Noosa Heads - I would be very curious to know what route the GPS systems tell ppl to go.

My TomTom One says to turn right at Noosa Drive, left on to Sunshine Beach Road, right on to Cooyar Street and then right into Lanyana Way. 5min travel time and 2.4km.

That was using house number 9 at Hastings St and 9 also at Lanyana Way.

Originally Posted by Dirty Doogie

I can test your GPS systems for you - free ! Your location is Hastings St Noosa heads QLD - your destination is Lanyana way , Noosa Heads - I would be very curious to know what route the GPS systems tell ppl to go.

Hastings Street
Left at the roundabout onto Noosa Drive
Straight at the roundabout
Straight at the roundabout
Left at the roundabout onto Sunshine Beach Road
Right at the roundabout onto Cooyar Street
Right at the roundabout onto Lanyana Way

But whoever blindly trusts a computer is going to end up in the wrong place.

Thing is, you don't. It gets you there. Every time. It might not be the original route, but it gets you there. Hasn't failed me yet, even when the street I wanted had been diverted and the original entrance now a house. Reading Street Port Macquarie.

The only time it actually led us astray was when I had changed the destination and forgotten to reset it. Fortunately I realised before we got too far in the wrong direction - my fault not the GPS.

And please stop using the world 'blindly'. You need to credit us with a bit more intelligence than that. It's also offensive to the visually impaired.

My faith in it is based on the fact that it has agreed with me on the routes I know and has not gotten me lost on the routes I don't. It's a faith based on observation, not blind optimism.

Hey thats cool! Dj and Silent C - both ur gps in top form - Over the xmas break certain GPS were sending ppl up steep hills near the lookout (circuitous but actually faster in holiday traffic) and in the rain they would go off the road and down a bank.

I don't know much about how the algorithms work but for it to be effective you'd have to imagine that it takes into account time of day and day of week. It would be interesting to see how much logic is actually in there and how much is just hard coded from people driving around and timing their trips etc.

It tends to overestimate the duration. For example the 6:00 quoted from here to Sydney is actually more like 5:30 - but I sit on just over the speed limit all the way. I don't think it factors in rest stops either.

However, we stopped at Canberra for dinner on the way up and as we walked out to the car, it was saying we'd arrive at Sydney at 10:48. As I walked in the front door, it was just ticking over to 10:48 - that also included the time it took to get the kids out and grab the bags but I reckon that's pretty bloody good.

There was story in the local paper about all the accidents that the police put down to ppl following certain GPS routes. drivers would leave Hastings St and, following the circuitious route, suddenly find themselves on a little narrow road in the middle of towering rainforest.

They would miss the street they had to turn into and realising their mistake try and turn around on the narrow road, but as soon as there drive wheels went off the bitumen they slipped and ended up down a bank.

In the article Police investigators put it down to the "feed back" type systems where drivers tell the GPS provider that the routes are too long /congested (time wise) . The GPS system looks at maps and devises another route. The short trip to Cooyar St can actually take 25 minutes in holiday gridlock periods. So it seems natural ppl would complain.

Quite interesting methinx