Sat Nav route finding

  SparkyJack 09:08 11 Jun 2012

I posted this on the Mobile forum a moment ago as it is more mere curiosity than a quest for assistance I though it may have a p0lace here also ---------------------------------o0o-----------------------------------

I have so far avoided acquiring a Sat Nav device simply relying on knowledge and a dog eared ancient UK atlas.

Then I purchased a Tablet-- and to play around to learn its foibles

It collects Sat Nav data from the mobile source.

So I set too. to plan a journey from my town to one that I know very well and its many routes of access.

The result led me all around the country side and motor way- when in fact there are several shorter less intricate routes.

I wondered how the 'logic' or route finding works.

It is little wonder truckers get stuck up alleys

Read more:

  spuds 09:30 11 Jun 2012

With my sat-nav, it give you the option of the 'pretty' route, the 'shortest' route or the 'motorway' route etc.

As to the logic, then its left to the satellites, which might not understand the council are digging up a road, and there is no entry?.

We had a local farmer who increased his income, by fishing out vehicles from the local ford. The council put extra signs in place and a barrier up!.

  interzone55 10:00 11 Jun 2012

Sat Navs use a few different methods to plan routes, but they all use the following logic

Find the biggest capacity road for the bulk of the route - ie motorways and A roads. It works in a similar way to how traffic is routed between nodes (routers) on a large network.

This may not be the most obvious way if you know the area, but if you know the area then you don't need a Sat Nav.

I have one that I only use when travelling somewhere new, or where I don't know the area. It has a TMC module that picks up traffic alerts and re-routes round traffic jams. It's also quite smart and uses different routes during rush hour.

  interzone55 10:01 11 Jun 2012
  Noldi 15:06 11 Jun 2012

Last weekend used a sat nav to guide me to a hotel car park in Brighton. It tried to send me down busses only roads and one way streets the wrong way, these roads are not recent changes. Very disappointed with it. I have used sat navy's for years but this is the first time it's done this.


  SparkyJack 17:52 11 Jun 2012

Thank you for the Link Alan Very informative/

  Blackhat 18:19 11 Jun 2012

I have only been in a vehicle using sat nav on one occasion. I accompanied my works delivery driver to help him off load, on the way back we needed fuel so I asked him if the sat nav had details of petrol stations, yes he replies and promptly pushed a few buttons and we followed directions.

I was familiar with the area and knew we were not heading for a petrol station, as I expected when the thing said you have arrived at your destination we were at the entrance of a fuel distribution depot, had we been a fuel tanker we might have got in.

  Snec 19:38 11 Jun 2012

I'm an avid Sat Nav user but just two days ago it let me down for the first time.

I was in an area I did not know at all when I came to this roundabout, way out in the country, and followed instructions for the road off and: Recalculating, Recalculating. I wondered how on earth I'd done that, momentary lack of concentration perhaps.

I returned to the roundabout and on using a different road achieved the same result. In fact whichever road I chose got the same result. I worked out, after a bit, that the Sat Nav thought there were at least five exits off the roundabout when in fact there were only four and it had not got a clue where we were anyway. BTW, this roundabout and the connecting roads looked as if they had been there for years, not new, or even newish, at all.

Don't carry a map book these day so in the end I just went along any old road, to get away from the roundabout, and it got itself sorted out at the next junction. Good job I wasn't in a hurry.

  SparkyJack 08:43 12 Jun 2012

I like the phrase 'Any old direction ', when lost

This is exactly what I do eventualy to arrive at a sign posted junction to sort one self out

  Chegs ®™ 09:08 12 Jun 2012

I used to joke about my satnav's inability to take me home via the most direct route,having read alans link,I now know why.My satnav uses the A roads I understand,but why does it then take me down into the town,along a badly eroded pothole infested secondary road,along another secondary road where parked cars impede progress onto another secondary road before finally informing me to turn left into a cul-de-sac instead of into my own street when it could simply tell me to turn left a few miles earlier on the A road,turn right and right turn again into my own street?If I'm approaching from the north,it does a good job but whenever I approach from the south it insists on taking me several extra miles out of my way.I know the area well so I just joke about it,but I've had to go and locate friends travelling to see me as their satnav has got them completely lost.I also did an experiment(as an unclassified road had been closed for 6mths due to an 38 ton HGV getting stuck on the two hump-backed bridges and destroying one trying to turn around)with my satnav,and the HGV driver stated his satnav had taken him along that route so I tried with my own & it took me along the main A road.Methinks the HGV driver was blaming his satnav rather than looking like a total pratt(and failed because he still is a pratt for trying to negotiate a narrow,winding country lane in a large truck)

  spuds 10:13 12 Jun 2012

Anyone who becomes totally dependent on sat-navs and on-line route finders will one day come in for some very big surprises.

Last year I used the MI, and was instructed to leave the motorway at junction 15a for Wooton (a place I wanted), both by pre-printed route finder and sat-nav. The good old (latest version) road atlas suggested that I should leave the motorway at junction 15. Guess what was the easy route, saving a cross country journey and half hour extra on finding the place I wanted. On arrival I did need to use local knowledge, because the actual place was not exactly on the sat-nav, and was hidden away. Considering that the place was used for many years by the MOD, it wasn't bad going?.

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