Route calculation data

Kenny Rodkiss

Well-known member
UKGSer Subscriber
Jan 6, 2002
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Scottish borders
Or Autorouting,

with reguard to map sizes with this box ticked or not.

I do not think I have ever ticked this box when selecting and then saving maps to my SP111 yet it still takes me to where I want to go talking me through the route turn by turn, ie Autorouting. ??

Has anyone found a difference in opperation of their gps with or without this ' route calculation data' box ticked.

:confused: :confused: :confused:

If you have the appropriate basemap for your area (meaning, you are using a European SP III with the Atlantic basemap installed in it within Europe), the SP III will still be able to autoroute you, using the basemap data, even if you have chosen to not download the additional routing detail from your CityNavigator CD.

The routing you get from the basemap only will not be as precise as what you would get from the map detail provided by CN - the basemap does not contain attributes about road speed limits, number of traffic lights per mile, etc., nor does the basemap contain the smaller streets.

But, if you just wanted to get, for example, from downtown Manchester to downtown London, the basemap alone would be enough to get you there, without needing to have autorouting data from CN loaded.

What you would probably observe, under these conditions, would be that the magenta route line showing your desired route would not exactly overlay the roadway when you zoom in to closer than a 3 mile scale. This will be especially noticeable when the "next turn" pages pop up - the magenta track line will appear as a series of vectors, rather than a curved overlay of the road. This is because the basemap contains "coarser" data than the detail maps.

However - for a person making a long trip with a SP III, who does not need super-accurate residential routing - this might be a workaround that would allow more map coverage (in square miles) to be loaded onto the chip. The only other downside, besides the rather coarse vectors you will get from the magenta route line, is that the basemap detail is older (ca. 1999-2000) than the CN data. So, you might see some improbable routes, if a new major roadway has been constructed in the last few years - the basemap won't know about it, and won't route you over it, but you'll still see the newer roadway displayed on the screen.

This information is also applicable to the GPS V and SP 26xx.

I know what you are saying as I have occasionally, while on holliday, not had all the maps loaded for a tour, ie missing out one or two maps on a route because there was little chance of going off route, and when you go from a loaded map to the base map you notice the drop in accuracy and detail.
Plus it only tells you to drive North or East and not turn by turn.

What I was asking was that I have not knowingly ticked the box for 'route calculation data' ever, yet I still get street by street detail and routing with voice commands as when to turn.
I ask because of the size difference when loading the maps onto the data card.
I can get almost all of the UK onto a 128mb card.
Without a tick in the 'route calculation box' comes to 78.8mb.
With the tick it comes to 123.4mb.
I take it I must be loading 'route calc data' or it would not be calculating my routes?
Sorry if I am not making sense.


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Good question I look forward to the answer

I must admit I have never noticed that box as I have never had autoroting before (I owned a Streetpilot ColorMap), but now I have the SP111 it will be intersting to know. I may even have to download the data onto my card again:confused:

Good Question Kenny.
Kenny, the picture you posted above shows the mapset selected and the box for the check mark to "Include Route Calculation Data" empty. So, if you saved that to your GPSR or data chip as a mapset, in theory, you would not have the info needed to provide detailed route calculation data.

Perhaps it is possible that when you leave this check-box empty, only the 'invisible road attributes' are removed from what is loaded to your data chip. In this case, the GPSR could still auto-route you using the CN or CS road data (right down to the smallest street), but it would not have the additional information about speed limits, number of traffic lights per mile, exact wording of overhead signs, etc. to calculate the best possible route, or give the most precise guidance when driving on multi-lane roads.

Looking back at my original answer (2nd post) to your question, I just realized that I responded to you as if you were not loading the map segments at all, rather than not loading the 'road attribute' (route calculation) data that goes with the map segments. Sorry about that, I am glad you followed up and clarified it.

It might be that you have just discovered (by accident) something that will help other users who have limited memory card space. I am thinking in particular about Adam, who is concerned about the increase in size of CS 6 over CS 5 for use on his GPS V.

Adam, why not give this a try? Load the CS 6 data without the route calculation data box checked, and see what kind of results you get. Might be a pleasant surprise.



I just loaded one map tile and did NOT tick the 'route caculation data' box.
When I reinserted the data card and switched on I got a warning that 'route caculation data' was not available with the loaded map.
I still got all the map detail but any attempt at asking it to route was a waste of time.
It was just the same as working from the base map with the route line going straight from one point to another and not following the roads.
If you roughly knew where you were going it makes a fine scrolling map.
She was pretty close with the verbal instructions mind you.

So the answer is that I must have loaded the route data in the past.:cool:

Amost know where I am now.....
If you change your Routing Preference to Off Road then you will get a straight line route which is surprisingly useful (even in town)

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