Driving Through Tunnels

Bazzer · Posted: Fri Jul 15, 2005 10:09 am Post subject: Driving Through Tunnels

When entering tunnels the signal is quickly lost (as you would expect) and then takes a little while before it reacquires the signal after exiting.

However, I assume that TomTom/TeleAtlas KNOW that the section of road on the route is a tunnel and would take this into consideration when giving voice instructions.

For example, when exiting the Mersey Tunnel (on the Liverpool side), you immediately have to negotiate a roundabout, but as the GPS has not reaquired the signal, it does not know where it is, and so does not give any instruction as to which to turn.

I would have thought (if the programmers are clever enough), that before entering a tunnel, it would give the correct instruction for when you exit, therefore keeping you on the correct route.

Or alternatively, in circumstances when it loses a signal, it automatically gives the command for the next instruction and the distance to it.

I believe that this enhancement should not be too difficult to implement. I think that am email to the TomTom Developers is in order.

Baz
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TomTom Go 50 - Going in the BIN
TomTom Go 730 (RIP)
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Garmin Oregon 45oT
Garmin Edge 1000
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jamiepyoung · Posted: Fri Jul 15, 2005 10:11 am Post subject:

sounds like a good idea - i had the same last week exiting the m25 for enfield - exit is virtually in the tunnel

CJackel492 · Regular Visitor Joined: Mar 15, 2005 Posts: 210

I thought that when you entered the tunnel and lost signal that TomTom would then estimate your position by using the last speed before the signal loss, So therefore continue to navigate you until it got a signal back?

I'm sure I noticed it a few times that it wold still show me moving through the tunnel?

Might have been TTN3,

Carl,
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Phones - Nokia 9500 + a few others
Nokia 9500 running TTM5 Sad

Bazzer · Posted: Fri Jul 15, 2005 10:36 am Post subject:

I'm still using TT3 (waiting for upgrade to TT5), and after it has lost the signal, the map screen just hangs stating 'GPS Unreliable' until it finally reacquires the signal upon exit.

Unfortunately, it does not continue to navigate.

Baz
_________________
Garmin DriveSmart 61 LMT-D
TomTom Go 50 - Going in the BIN
TomTom Go 730 (RIP)
Garmin Montana 650
Garmin Oregon 45oT
Garmin Edge 1000
Tracklogs Digital Mapping

MarkHewitt · Posted: Fri Jul 15, 2005 10:54 am Post subject:

chaddow · Occasional Visitor Joined: Jun 07, 2005 Posts: 25

Having driven through a number of tunnels on a recent trip to Spain with TT5 it would appear that TT5 estimates your position for about a minute after loss of signal and will during this time issue direction messages, e.g. if there is a roundabout or whatever if appropriate.

After the 1 minute TT5 seems to stop estimating poistion or issuing directions until the signal is reaquired.
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uk89camaro · Regular Visitor Joined: Jul 04, 2005 Posts: 113

I believe there are some systems about that have additional sensors attached to the vehicle wheels, that can provide "tunnel support" until a GPS signal is re-acquired.

Tom-Tom is not one of them.
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Tom Tom 1005 v2 World, Garmin Dakota 20, IPhone 4S

Oldboy · Posted: Fri Jul 15, 2005 8:44 pm Post subject:

Diplo · Posted: Fri Jul 15, 2005 9:05 pm Post subject:

CJackel492 · Regular Visitor Joined: Mar 15, 2005 Posts: 210

And I thought they used accelerometers?

Carl,
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Phones - Nokia 9500 + a few others
Nokia 9500 running TTM5 Sad

linknet · Frequent Visitor Joined: May 05, 2005 Posts: 872

uk89camaro · Regular Visitor Joined: Jul 04, 2005 Posts: 113

linknet · Frequent Visitor Joined: May 05, 2005 Posts: 872

Diplo · Posted: Sat Jul 16, 2005 12:38 am Post subject:

7andy · Regular Visitor Joined: Jul 02, 2005 Posts: 74

GPS units can also be a little clever when they lose signal. My Garmin 12 continues at the last known parameters for up to 15 seconds before giving up, perhaps fooling Navigator into thinking it still has a perfectly good signal!!

Cheers, 7&Y

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