TT Traffic Vs RDS-TMC

zzr1200 · Posted: Wed Mar 12, 2008 8:47 am Post subject: TT Traffic Vs RDS-TMC

Hi,

I've been using my PDA with TT Traffic over the past week as my TT720 has been sent back to TT for repair.

What a revelation?

It actually reports lots of traffic info, mostly correct. When I use my RDS-TMC with my TT720 it never shows up as much info.

OK, I use the M4 a lot and I have a massive hole where I get no reception (Swindon to Reading, is this the same for everybody else?) but The difference in information was astouding.

I do get a full green ball using my RDS-TMC so what's different?

Any help most appreciated.

perussell · Frequent Visitor Joined: May 12, 2006 Posts: 292

Previous satnavs I have owned have all had a black hole between Swindon and Reading when using RDS - TMC.
However as you suggest TT TRaffic via GPRS seems to be much better. I purposely bought the non-T version of the 720 and despite some initial hiccups in pairing the device with my phone now receive a much more reliable signal.
The data quality does appear to be slightly better than via RDS-TMC though it is still highly questionable on more than enough occasions . Roadworks are represented fairly reasonably but congestion reporting is still poor.
If they could only provide reliable data for perhaps 90%+ of the time this would be almost as good as it could get.(see my post in the ITIS thread)

Darren · Posted: Fri Mar 14, 2008 11:30 am Post subject:

There are two issues at play here. The actual data is the same whether delivered by GRPS or FM.

Reception via Fm has some effect as it may not receive all messages if th signal is weak or absent completely. But the x20's have a bug where they don't correctly handle TMC messages. What the exact cause is we haven't identified and TT are tight lipped on the subject although they acknowledge there is an issue.
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perussell · Frequent Visitor Joined: May 12, 2006 Posts: 292

DennisN · Posted: Fri Mar 14, 2008 12:07 pm Post subject:

There is a difference in what is transmitted to you - GPRS sends you everything it's got for the whole of the country. FM sends you what it's got for the "local" area covered by the transmitter. For example with FM you might only get South West until you approach the next transmitter, whilst with GPRS you'd get the whole country. I'd prefer the whole country, because I can easily need to drive from Bristol to Aberdeen and if there's trouble up that way, I might wish to re-route via M1 instead of M6 and that's easier from down here than suddenly getting a problem when a diversion would take me amongst all the other diverted traffic on a close parallel route.

But the real problem is that the RDS-TMC information is not even remotely reliable when it reaches me - I've had it forecasting huge delays for a simple lane closure, or a mere one minute for a motorway accident complete closure. Just not worth using.
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zzr1200 · Posted: Fri Mar 14, 2008 12:58 pm Post subject:

Well I've got my TT7720 back after repair and it's a different machine as far as traffic is concerned!!!

I plugged my RDS-TMC into the unit and it locked on outside my house in a matter of seconds - I've NEVER managed reception there ever before.

Drove from Gloucestershire, along M4 (usual blackspot for me) into central london and back. I reckon I had the green ball up for 92-94% of the time AND it was given me reports of traffic!!! Can't beleive the difference. Obviously had a big fault with my TT that made the TMC look like it was working poorly beforehand.

PS - I haven;t moved my aerial at all so that cannot be the reason.

PPS - New motherboard was fitted to my TT720.

wazzzzupmate · Posted: Tue Apr 15, 2008 7:23 pm Post subject:

So you are part way there. You say the 720T displayed traffic info. Did it put times along side the delays?

AndyVaughan · Posted: Wed Apr 16, 2008 7:57 pm Post subject:

If you look here and scroll to the bottom, TT state

andygarmin · Lifetime Member Joined: Dec 04, 2003 Posts: 4

I've been using TT traffic with a 720 for a while now. never bothered with the TMC system as I have had other GPS systems before that had TMC and they were all rubbish. TT Traffic is great. Soon as I set navigation, it connets to my N95 and downloads the update. Very accurate and has saved me a lot of time recently.

Interesting that the 720 can connet to my N95 even while the phone is still connected to a bluetooth earpeace. i thought you could only connect to one bluetooth device at a time.

perussell · Frequent Visitor Joined: May 12, 2006 Posts: 292

I can concur with the above. Have been using a Go 720 with TT Traffic via GPRS for a few months now and find the actual transmission of data to be far more reliable than RDS-TMC. It is much more reliable in forecasting traffic congestion though my only gripe would be that it tends to over-estimate the likely delay e.g. delays of 20 minutes have been less than 5 mins in reality but that may be due to the transitory nature of traffic congestion.

Kremmen · Posted: Fri May 09, 2008 11:05 am Post subject:

mikealder · Posted: Fri May 09, 2008 12:25 pm Post subject:

The TomTom system gets its data from iTIS Holdings who use use Classic FM and a few other transmitters across the UK to deliver the data. The data sent out is regional, for example living in Blackpool my device will display data of incidents right across the country but only as far North as Carslile, and South to around Stoke.
When moving the device automatically re-tunes to different transmitter frequencies which will be broadcasting more regionally biased information. The idea being you will receive data for the area you are heading towards well before you actually get there.

Your inbuilt car system might use TrafficMaster as the data provider who operate differently to iTIS - Mike

Kremmen · Posted: Fri May 09, 2008 2:51 pm Post subject:

I knew there had to be a reason - ta

I have been into the Honda diagnostics whilst it's acquiring it's TMC fix. It initially rotates around all the stations on the radio preset list to see if any have TMC data (or TMC provider as it's named in the diagnostics).

When it's finished it displays the 'provider count' and 'signal strength' then picks the strongest signal and sticks with that. The traffic info is almost immediately available.

I bet that at 16:30 when I set off for home (Friday rush) the 'Traffic Event List" has a tiny scroll bar and the furthest event, way down the bottom, is probably Edinburgh or similar which is not a lot of use when I'm in Surrey Smile

In my area it starts off using Eagle radio then switches to Capital radio as I get near to Heathrow.
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mikealder · Posted: Fri May 09, 2008 2:53 pm Post subject:

Kremmen · Posted: Fri May 09, 2008 3:04 pm Post subject:

I was obviously under a false impression that all RDS-TMC came from the same source, ie local radio station.

That's that cleared up.
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