RDS traffic and GPRS

playswell · Regular Visitor Joined: Feb 23, 2008 Posts: 91

Hi I have the tmc modual for my Go 720, but also recently subscribed to the GPRS version as well. A couple of questions, if i plug the TMC modual in and its in a bad reception area will the gprs take over? And I will be using my work phone for the data, I have set the updates at 4mins, is that reasonable? Or should i make it say 15 mins, I dont want the company complaing of huge data costs, i travel on average about 4 hours a day

mikealder · Posted: Sun Jun 08, 2008 8:07 pm Post subject:

As soon as you plug in the RDS-TMC device this will take over the device, it will not use GPRS based traffic at all, even when you loose the FM derived signal - treat it as one or the other, if you have paid for the Subscription service and don't mind paying the costs of the download via your mobile phone then use it - leave the RDS-TMCdisconnected. The mobile phone derived service is far more reliable in terms of reception than RDS-TMC will ever be in the UK - the data comes from the same place so there are no differences there - Mike

playswell · Regular Visitor Joined: Feb 23, 2008 Posts: 91

mikealder · Posted: Sun Jun 08, 2008 9:00 pm Post subject:

15 or even 20 minutes is more than sufficient IMHO, from the time an incident occurring to it causing a problem that is picked up and broadcast for your unit to receive will probably be at best 20 to 30 minutes so why hammer the GPRS and associated cost.
I use 15 minute updates which tend to average out around 100KB per hour - that’s 1MB for every ten hours driven, this figure can go up or down depending upon the time of day and traffic conditions but it is a good rule of thumb.
I would contact your phone provider and ask them to specify how much the GPRS data traffic costs when used as each network has different tariffs, I use an unlimited tariff but still don't use any faster than 15 minute updates as I see little point - Mike

rtj70 · Regular Visitor Joined: Jun 18, 2005 Posts: 144

If there is new data and your unit has not picked it up then the traffic status icon will change from a green circle to a yellow one. You can then update manually if needed.

Thermocline · Posted: Mon Jun 09, 2008 11:42 am Post subject:

Hi Guys

Perhaps I'm misunderstanding something here. I had quite a long chat with TT customer support a little while ago regarding the Latest Map Guarantee issue. While I was speaking with the agent, I took some time discussing the differences between the two traffic systems.

What I understood is that the RDS TMC system is run by whatever agency and is pretty much just the same sort of information you'd get by tuning into the Traffic broadcasts on the radio Further, the RDS TMC system was limited to the region of the country you happened to be in. For a long route, traffic would only be considered for the part of the journey that was encompassed by the region you are currently in. A trip from Scotland to the South of England would only consider traffic in Scotland. Assuming coverage was available, that data would be updated as you travelled from one region to another.

On the other hand, the GPRS traffic data (I was told) is not derived from the same data as the RDS TMC system. The GPRS Traffic data is a different set of information which is managed by TT themselves. I definitely got the impression that I was being told that the GPRS data was much more accurate and complete. Further, the traffic data would cover the whole planned route, regardless of regions. Discussing this issue further with the rep, I sort of got the impression that TT buy traffic data from Traffic Master. I was absolutely assured though that the quality and accuracy of the data would be far better with GPRS than with RDS TMC.

In my opinion, if the data for both system was exactly the same, why would there even be a reason for subscribing to the TT GPRS traffic system unless you couldn't get a decent reception for whatever reason.

As I said, the above is my understand of the situation following a discussion with TT customer service a short while ago. I Would be happy to be corrected as I am giving serious consideration to subscribing to the GPRS traffic service in the near future.

mikealder · Posted: Mon Jun 09, 2008 12:40 pm Post subject:

The data is the same and comes from iTIS Holdings TomTom do not get any data from Traffic Master this applies to both RDS and GPRS.
You are correct that GPRS data covers the entire country whereas RDS is regional, but the region covered is quite large, I can see hold ups as North as Carlisle and as South as Birminham from Blackpool when using RDS. - Mike

playswell · Regular Visitor Joined: Feb 23, 2008 Posts: 91

rtj70 · Regular Visitor Joined: Jun 18, 2005 Posts: 144

This is how it worked on TomTom Navigator 5 which I used on my iPaq for years... but looking at the manual they seem to have taken this functionality away. Now it just says how out of date it is. Again TT taking away something good. Probably due to it not being able to share the code with RDS traffic updates? Yellow on RDS-TMC traffic means looking for a station.

For TT5 it used very little TCP/IP traffic over GPRS to discover there is more up to date info - and I've not checked but this might even be sent to the device. But it did not automatically download any new information about traffic hence only warning you it is not up to date.

playswell · Regular Visitor Joined: Feb 23, 2008 Posts: 91

rtj70 · Regular Visitor Joined: Jun 18, 2005 Posts: 144

It did on TomTom Navigator 5 but it looks like it doesn't on the GOs now. Which is a shame and I was wrong. Setting to 15 minute updates seems to be fine anyway though. And if set more frequent it does not use much more bandwidth because if there's no updates to download then there's little data to download.

mikealder · Posted: Mon Jun 09, 2008 9:05 pm Post subject:

The PNA devices now work slightly differently to the PDA software:

When using the RDS-TMC device:
On the 720 running version 7,480 or higher you will see a rotating arrow top right of the main screen while the unit is looking for a signal, once it finds a signal you get a full green circle which denotes the device has at least had a sniff of what it is looking for.
You do not get an amber disk any longer, if the unit fails to receive any data for 5 minutes the disk goes one quarter grey, after 10 minutes it is half grey, 20 minutes and it is a totally grey disk.

When using the GPRS based service I would never expect to see anything other than a green disk as reception shouldn't be an issue - Mike

JaguarV12e · Posted: Mon Jun 09, 2008 9:28 pm Post subject:

rtj70 · Regular Visitor Joined: Jun 18, 2005 Posts: 144

I use PAYG SIM in an old phone for GPRS traffic - the work phone does not have GPRS enabled and never will because they give "data cards" for mobile mail.... £10 lasts quite a while.

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