Sat Nav routing / updates

[petergl1800]

Hi,
I have a XJ358 (2008) and my sat nav leave a lot to be desired!
I put a route in and off it goes, but, and this is the problem, it does not send me on the route which I know is shorter and faster!
Why not? I was told that this is a 'Jaguar' problem of a poor sat nav, does any one know of this or have any ideas on how to correct this problem?
Thanks
Peter

[ptjs1]

Peter,

Perhaps a PO HS changed the settings to avoid motorways etc? Also, when it comes up with the 3 route options, is one of those options your preferred route?

Paul

[PaulGover]

All Sat Navs have to compromise on how to choose a route. Ones connected to the internet can update themselves to allow for traffic conditions, temporary closures, and whatever, but even then they don't know what the situation will be in say 1 hour into your journey. The factory-installed one isn't online, and the last map updates were issued in 2011, and so record the state of the roads in 2010, so if your faster route used newer roads, that would be one reason. Another depends on what information the map contains about the roads, and what algorithms it uses for estimating the "best" route.

There are two issues here: online route finders like Google and Tomtom get feedback from some road users to let them plan using recent transit times between junctions on the maps, so their estimates will be pretty good most of the time (though dreadful when they've just diverted say the whole M40 round an accident via a single-track toll bridge, which they did to me a few years ago). I suspect the maps used in the fitted unit just have road classifications (motorway or similar, A road, minor road), and assumed average speeds down them. Certainly in the past "AutoRoute" worked that way - originally with a vast plethora of classifications (as above, but with a separate sprinkling of "urban" and "rush-hour" settings), which let you tune it to your driving expectations. When Microsoft bought them out, they simplified it by removing most of the options (there were too many), which meant the time estimates were worse, but the choice of "best" was still reasonable.

The other half of the equation is the "cost" function - the routing algorithm finds a route that minimizes the cost, where cost might be simply minutes (for quickest route), distance (for shortest), number of changes of road number (for simplest), or some more complex mix of any of those or other factors. The fitted unit seems to have 3 cost functions; the first is quickest, the second is shortest, and sometimes I've seen a third, and I've no idea what that is. It's "quickest" is overly-keen on motorways - for Banbury - Southampton (about 80 miles straight down the M40/A34/M3) it chooses to go M40, M25, M3, about 50 miles further, because it thinks the A34 is significantly slower than a motorway. Conversely, the shortest from Fareham to Hedge-End shops (about 10 miles on a couple of A roads), it deviates from the A roads to go through a council estate, over speed humps, because it can save about 10 ft going shortcutting a roundabout.

There's another twist: it appears to use a simplified map for the "big bit in the middle" of any long route, probably ignoring minor roads, to make the search quicker. and then the full map to get from there to the nearest major road junction. So if your start or destination point is a bit off the beaten track, it can make some bizarre choices.

The fitted unit has one advantage over stick-on ones; it has a compass, and it's coupled to the odometer, so it can do "dead reckoning" when there's no satellite signal; I think that also helps it improve the "distance to turn" calculation, so if you watch the "thermometer" bar on the display it usually locates the turn to within a few feet, both of which help in cities.

[petergl1800]

Thanks very much for the info, I will look into it.
Kind regards
Peter

[Davidqhog]

Stirring an old thread.

My newly acquired Super V8 has the Navigation feature. It shows me where I am without fail.

But, I can't set Home or any Destination by any normal means. I did eventually set Home by going to the map and setting it that way. But for destinations, I click on Postcode or Address and it goes no further. I have never seen the virtual keyboard come up to enable me to set anything.

Also, occasionally, the Search Area (normally UK highlighted) shows no area in the EU highlighted.

Is this a function of the DVD in the slot (dated 2009 I think) or is the system dying? Anyone else seen this problem?

Many thanks,

David Q

[Davidqhog]

SOLVED IT!

Looking at another thread, I hit the system defaults, changed the area back to UK and, hey presto, the destination setup now works a treat.

Thanks to all those who went before - something about standing on the shoulders of giants!

Regards,

David Q

[Davidqhog]

Then, another issue!

Set Home and a destination locally, about 8 miles away, just to see what it would do. After calculating, it showed 4h 55m and 255 miles! When it displayed the map, it was still routing from its previous home in eastern Cambridgeshire.

Do I have to disconnect the battery and do a hard reset to clear everything. Apart from the radio, will I lose anything else (I have the code!)?

Regards,

David Q

[davidr]

If you do a hard reset (switch it off and on again in normal speak!) I'm not sure if that will lose the sat nav settings. What you will lose is the radio (but you have the code) and the learned settings like the gearbox change strategies.