Slow Route Planning

[reaps2000]

Hello All,



I'm currently getting some very slow route planning on my Ipaq 3970 (rom 2.00) and 256MB SD card (formated, fat32 32kb).



Could someone plan a route from Great Yarmouth Borough Council to Tickhill Road, Rossington (doncaster). It takes several minutes for me but calculating the reverse route only takes about 35 secs?????



Thanks

[Oldie]

Great Yarmouth Borough Council to Tickhill Road DN10, Rossington (doncaster). 60 secs



and 75 secs for the reverse route. Using TTN 2.20 with Route planning: Calculation: Fast



Ipaq 3970 (ROM 2.00) and 128MB SD (need to check format)



Richard

[DavidW]

You were ambiguous as to which Tickhill Road you meant - but I presume you mean Tickhill Road DN11 as that appears to be in Rossington itself.



Using "Quickest Route" with the default speeds, the full UK map and version 2.22, on my hardware it took:



97 seconds to plan the forward route, which came out as 160.2 miles, 3:19:45 duration.



58 seconds to plan the reverse route, which came out as 159.8 miles, 3:17:50 duration.



(comparing the routes carefully, it seems the difference is down to the one way system in Great Yarmouth - I know, first hand, there are quite a few restrictions in that area).





My understanding of the routing behaviour in 2.22 (and probably earlier versions as well) is that Navigator plans from the end to the start of the route. In an earlier thread we talked about routing from A'Chill (Highland) to Zennor (Penwith). There is no route, as A'Chill is on an offshore island.



If you try to plot the forward route from A'Chill to Zennor, you get the bar going all the way across to the end, with only a handful of miles remaining, before you get the "No route found" error. If you attempt to plan the reverse route from Zennor to A'Chill, you get the error straight away as Navigator apparently finds straight away no route off the island.





It seems, then, the speed of routing is dependent on the complexity of the road network at the destination of the route. There has to be a trade off between the last ounce of optimisation of the route and the speed of route planning, as routing algorithms have to take an essentially educated brute force approach (mathematics shows there is no outright way to calculate the best route). Because of this trade off, the two routes differ.





I suspect that there's more options to investigate leaving Doncaster heading in the rough direction of Great Yarmouth than there is leaving Great Yarmouth in the rough direction of Doncaster. This would accord with my experience of the roads; there aren't that many main roads in Norfolk and particularly out of Great Yarmouth (not least because of the Broads), whereas there are many routes out of Doncaster.



If the increased number of options comes later on in the route, then it would seem right that route is planned quicker, as obviously the location you find yourself having to plan from will reduce the number of options that have to be tested.





I have no knowledge of the route planning algorithms used by Navigator (I suspect they are treated as a closely guarded trade secret), so all I can share are my empirical observations.







David

[reaps2000]

Just measured my exact times,



Great Yarmouth Borough Council to Tickhill Road DN10, Rossington (doncaster) = 210 secs



reverse = 51 secs



Can't work out why there is such a difference....

[aero]

For comparison using: TTN 2.22, Ipaq 3970 ROM 2.00, Maxell 128MB SD Card with full UK maps installed.



Great Yarmouth BC to Tickhill DN10 - 45secs, return - 44secs



Great Yarmouth BC to Tickhill DN11 - 55secs, return - 32secs



Both outward and return journeys equate to 159.7 miles, duration 2:29:10 (I checked this several times)





What about the speeds set for each type of road? Mine are not set at default (as you can probably guess if you compare my journey times to DavidW's!!)

[DavidW]

I had Normal calculation selected, road speeds at default, and I asked for the Quickest Route. I'm using the full Great Britain map, software version 2.22 and timing from pressing OK to the Route Summary screen appearing. Hardware is an iPAQ 3970, map on a SD card.





Repeating for Tickhill Road, DN10 (only bothering to quote calculation times):



Outbound: Strict 2m24s (144s), Normal 1m25s (85s), Fast 50s



Return: Strict 1m41s (101s), Normal 1m15s (75s), Fast 1m (60s).





Yes - the results for Fast are the right way round!







David

[aero]

<dull mode on>



I'm not sure what this 'strict' setting is, what it does or how I access it.



Can anyone tell me?



<dull mode off>

[reaps2000]

I decided to hard reset and start over to see if that would cure my problems.



Running on TT 2.00 or 2.02 it only takes 55-59 secs to do the Yarmouth to Doncaster route.

As soon as I go to TT 2.22 its back to 210 secs again.



I'm a field based engineer and travel all over the country and have only noticed this slow down on this one route, but it's only happening when I use TT 2.22. So I assume that TT have made some adjustments to the routing.



I'l stick to 2.02 for now I think....



Thanks for all the replys

[DavidW]

aero - check the Properties screen, Advanced tab. There's various settings there, one of which sets the routing preference to either Strict, Normal or Fast.



reaps2000 - the routing algorithms are tweaked somewhat in 2.22 according to TomTom. Sounds like there's some nasty interaction going on with your set up! I can understand you reverting to an earlier version.







David

[aero]

Thanks David.



I don't have any complaints about the routes TT plans for me at the moment. What affect will changing route preference have?

[DavidW]

I think Normal is designed to be just that - the normal setting. Strict may give you a slightly more optimised route, at the cost of greater (sometimes significantly greater) calculation times.



Fast, on the other hand, may give you a slightly less optimised route that is calculated more quickly.





If you're happy with the routing on Normal, I'll probably leave it on Normal. I'm going to run with Strict for a while just to see if I can notice any difference. I don't expect I will!







David

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