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Posted: Wed Nov 19, 2008 7:24 pm Post subject: Re: Underwhelmed by IQ routes
Guinness2702 wrote:
Therefore, to calculate data for the whole of the uk, to a granularity of 1km, you need approx 4 billion meaurements, and more realistically 40 billion down to 100m.
Posted: Wed Nov 19, 2008 7:37 pm Post subject: Re: Underwhelmed by IQ routes
Wishlist wrote:
Anyone know where I can buy a 400GB SD card?
Lol - Don't panic! - fortunately, all of the data samples will *not* be encoded in the maps, just the final averages - and you don't need 2016 data for each stretch of road as you could easily compress the data - e.g. for most of the time road X will be at xx mph, but between say 8.25 and 9.15 it will be yy mph, so you just record the two values and the time range.
I do hope that you have the option to send them data anonymously is enabled on your device then! The best way to improve this stuff is to enable the logging.
Yeah, definitely a good tip. As I said above, most people don't use their sat nav for regular journeys, but I make a point of not just submitting the data, but at using my sat nav for regular journeys, which should add to the data for the routes I travel the most. I would expect LIVE users to do that a lot more, since HDT and IQR ought to provide at least some motivation to use it for every journey, at least once the data starts to improve (although in my case, I doubt the routes are covered by HDT)
But does disabling 'send data' really work? It takes so long to connect/download using Home and uses so much processing power that I reckon it is reporting all my journeys - even with 'send data' disabled. _________________ Alan
Go 750 LIVE Europe Map 870.3406
Go 720 W Europe Map 865.3245
One XL W Europe. Map 715.1689
Dell Axim & TT3
Psion 5mx & Routeplanner
it already claims to have 'billions of data points'. Yet it adds a really, really silly amount of time on for rush hour. Some examples for you. It is currently around 9pm at night. Nice, quiet roads. Or as quiet as they ever get these days. I am planning the following journeys from my home to various city centres. Then I am doing an 'advanced planning' journey, telling it I am leaving between 6.40 and 8am so as the bulk of the journey takes place between 7am and 9am. I am always going for the worst case scenario here. We all know what it is like getting into a city centre at these times, so this seems like a fair test of IQ routes to me. For reference, I live just outside Derby. So....
Home to Liverpool NOW = 1.41 hours, 94.7 miles
Home to Liverpool leaving at 6.40am = 1.50 hours, 94.7 miles
Home to Sheffield NOW = 0.47 hrs, 44.0 miles
Home to Sheffield leaving at 7.40am = 0.53 hrs, 44.0 miles
Home to Lincoln NOW = 1.21 hours, 58.3 miles
Home to Lincoln leaving at 7.20am = 1.31 hours, 58.4 miles
Home to Leicester NOW = 0.51 hours, 39.2 miles
Home to Leicester leaving at 7.50am = 0.59 hours, 39.2 miles
Home to Leeds NOW = 1.12 hours, 72.3 miles
Home to Leeds at 7.30am = 1.24 hours, 72.3 miles
Home to Derby city centre NOW = 0.10 hours, 3.6 miles
Home to Derby city centre at 8.15am = 0.13 hours, 3.6 miles
It is clear that IQ routes is working, but I know from bitter experience that none of the above is valid data for rush hour. If HD traffic picked up the problem areas that IQ routes missed on 95% of occasions then it wouldn't be a problem. But I've been sat in the usual 20 mins for 1.5 mile queue getting into Derby on the A6 this week. IQ routes claimed I should already be there and Traffic was none the wiser despite being impressive in its knowledge of other A roads around these parts. And if it thinks that getting into Sheffield at rush hour takes only 6 mins longer than at 9pm it is dreaming!
Also interesting that on none of the above occasions did it re-route me; follow the link and it suggests that IQ routes will indeed take you around the traffic. Problem is at the moment that it is not realistic with its predictions and therefore does not see the need.
Also interesting that on none of the above occasions did it re-route me; follow the link and it suggests that IQ routes will indeed take you around the traffic. Problem is at the moment that it is not realistic with its predictions and therefore does not see the need.
Posted: Wed Nov 19, 2008 10:54 pm Post subject: Re: Underwhelmed by IQ routes
Guinness2702 wrote:
Wishlist wrote:
Anyone know where I can buy a 400GB SD card?
Lol - Don't panic! - fortunately, all of the data samples will *not* be encoded in the maps, just the final averages - and you don't need 2016 data for each stretch of road as you could easily compress the data - e.g. for most of the time road X will be at xx mph, but between say 8.25 and 9.15 it will be yy mph, so you just record the two values and the time range.
*sigh* still thinking too much.
Guinness2702, I found your calculation excercises interesting to read. What surprises me is that there is so little difference in map size comparing the v810 map with the v815 map. Even with smart compression algoritms, the enhanced IQ routes data should have made the data grow more than what it has done....unless TomTom have removed further details from the map in order to make room for the IQ routes data.
Any idea, anyone? _________________ TomTom GO720T: App ver 8.351(9982/090518), OS:315187, GPS v1.20, Boot 5.5120
TT RDS-TMC: 4V00.013
Maps: Scandinavia v840.2562, Western_Europe v715.1703
Garmin GPSMap 60CSx (SW ver. 3.70)
Posted: Wed Nov 19, 2008 11:07 pm Post subject: Re: Underwhelmed by IQ routes
uffe73 wrote:
Any idea, anyone?
Maybe the data was mostly already in the previous map too, but there was a metadata change required in 8.15 to make it work with the 8.300 navcore to give IQ2.
Posted: Thu Nov 20, 2008 1:03 am Post subject: Re: Underwhelmed by IQ routes
loriannod wrote:
uffe73 wrote:
Any idea, anyone?
Maybe the data was mostly already in the previous map too, but there was a metadata change required in 8.15 to make it work with the 8.300 navcore to give IQ2.
Pure hypothesis, of course.
I don't know what he meant by "little difference", but remember that the old maps would have had the road speed embedded for calculations - it is only for roads where the speed varies where there will be extra data, and if you were really clever about it (too late at night for me to do any thinking any more), but you could probably incorporate variations in as little as a few bytes - so if you only had one variation per km of road (remembering again that you probably don't have enough sample data for the majority of local roads), then you'd perhaps add as little as 1MB to the size of the maps - and even that doesn't take into account the already existing but older IQR which worked on a daily basis.
uffe - how much did the size change by, just out of interest?
it already claims to have 'billions of data points'.
...yes, but that's "worldwide"
For any one country, you're can perhaps infer from that that it is more likely to be measured in hundreds of millions, a long way shy of the 40 billion my rough estimate needs. And the majority of those hundreds of millions will be on major roads.
At a total guess, I'd say that 90-95% of journeys made where a sat nav was involved would be on motorways and major A roads - lets face it, for short/local trips, people are probably gonna know how to get there anyway, and until the advent of HDT, there's been little motivation to use a sat nav for those. So the vast majority of that data will be for those major roads, and there will be much less for local roads. Don't believe me? Look out of your window at your residential street - how many cars go past? Not many is it....and how many of those do you think have a sat nav in and turned on....and how many of those (whether they volunteer to share or not) actually plug the sat nav into their PC? - I'm a techy/geek, and *I* rarely plugged my old ONE into the PC - what chance the hapless masses?
EDIT - of course, I'm somewhat defeating my own argument a little, since if 95% of the journey is on well travelled roads with plenty of sat nav data, then for those roads at least, it should be fairly accurate - and I suppose that by definition, a regular morning traffic jam will have lots of cars in it, and a higher likelehood of data capture, and for the non-busy roads, you can just assume the speed limit is reached (speed humps aside), so really, it should in fact work quite well - now I'm disturbed, I'm arguing with myself, and I haven't even taken any drugs!
Posted: Thu Nov 20, 2008 7:47 am Post subject: Re: Underwhelmed by IQ routes
Guinness2702 wrote:
I don't know what he meant by "little difference", but remember that the old maps would have had the road speed embedded for calculations - it is only for roads where the speed varies where there will be extra data, and if you were really clever about it (too late at night for me to do any thinking any more), but you could probably incorporate variations in as little as a few bytes - so if you only had one variation per km of road (remembering again that you probably don't have enough sample data for the majority of local roads), then you'd perhaps add as little as 1MB to the size of the maps - and even that doesn't take into account the already existing but older IQR which worked on a daily basis.
uffe - how much did the size change by, just out of interest?
The road speed data could be done in very few extra bytes. Each road is currently classified by type yes? So Motorway, A road, B road, track. Thus each road is given an index into the table of road types, with speeds etc. Want to know how fast you can go on a particular road, look it up in the roads table using the type index.
Now, to do different speeds at different times, just expand the table. Instead of about 4 types, have 256 types, each with different profiles based on the most common timing profiles found in the data. You now have all that information in a small table, and no extra data stored against each segment.
Note that I'm not saying this is how it is done, it is just the first thought that came to me as to how I'd achieve all this extra info with as little space as possible.
Posted: Thu Nov 20, 2008 10:01 pm Post subject: Re: Underwhelmed by IQ routes
uffe73 wrote:
Guinness2702 wrote:
I don't know what he meant by "little difference", but remember that the old maps would have had the road speed embedded for calculations - it is only for roads where the speed varies where there will be extra data, and if you were really clever about it (too late at night for me to do any thinking any more), but you could probably incorporate variations in as little as a few bytes - so if you only had one variation per km of road (remembering again that you probably don't have enough sample data for the majority of local roads), then you'd perhaps add as little as 1MB to the size of the maps - and even that doesn't take into account the already existing but older IQR which worked on a daily basis.
uffe - how much did the size change by, just out of interest?
I will give you the exact numbers tonight.
A comparison of the three latest Scandinavia (Sweden+Norway+ Denmark+Finland) maps (v720, v810 and v815) gave the sizes 215 Mb, 221Mb and 223Mb respectively. For these three map releases the size of cline.dat was 75,1Mb, 81,1Mb and 85,3Mb. So, if we assume that all map changes between v810 and v815 concerned Sweden and came from the enhanced IQRoutes data, IQ Routes would use 4,2Mb to cover 539 979 km of roads. Provided that we have IQRoutes coverage of 10% of these roads with 100 m resolution, it would take 56.7 billions of measurements to cover all Sweden. Even with the compression algoritm in the world it would not be possible to fit that data into 4,2 Mb.
Joined: Feb 07, 2005 Posts: 171 Location: Cambridge UK
Posted: Thu Nov 20, 2008 10:50 pm Post subject:
I expect that Tomtom don't atempt to code discrete data points, but have an approximation function with a few (3 or 4) parameters that expand into an estimate of the time to traverse a section of road. Then when you apply compression to those paramters, they don't take much space at all.
Someone with more time that me could pick a road which has bad rush hour congestion, and put the IQ route times for a week into a spreadsheet and graph the times against time of day. I expect that you will get some nicely rounded curves.
I would then predict that the curves for any other road would be of similar shape. _________________ Tomtom Go 1005
Tomtom Go 730T
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Anyone know where I can buy a 400GB SD card?
