Mileage discrepancies

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CThody
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Joined: 23 Oct 2019 09:07
Great Britain

Mileage discrepancies

Post by CThody »

Hi. Thanks for letting me join this forum. Just got a 660 and downloaded Basecamp. Created a couple of routes and transferred to the 660. However, the reported distance of the routes is different between the Basecamp software and the 660 itself.

Any ideas why this might be?

Thanks in anticipation.
sussamb
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Re: Mileage discrepancies

Post by sussamb »

What sort of difference, and are you sure they are exactly the same? Look at the routes on the device using BaseCamp, easier to spot any discrepancies.
jfheath
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Re: Mileage discrepancies

Post by jfheath »

It is possible that the route is being recalculated when you import it into the 660. This will happen if the map on the Zumo is not identical to the one in Basecamp, also if the transfer settings in Basecamp are not set properly. By default i think it is set to strip shaping points, for example.

I think a little leeway is possible, but the two shouldn't be miles out.

Note that the 660 may have routing issues when a route is transferred from Basecamp, due to the fact that BC route files may have more data types than the 660 knows about. Introduced when the Trip Planner system of the 590/595/396 came out.

Today, I discovered something really important. I found another way that doesn't work.
Breezly
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Re: Mileage discrepancies

Post by Breezly »

There are several issues that can cause the route to differ on the GPS. Are your maps, preferences and avoidances the same on the GPS and in Basecamp? Are you using the same routing profile? The more important underlying question is how do you get them to be the same? First, use the same map, have all your preferences routing and avoidances set the same. Then when you create the route in Basecamp you'll need to add enough intermediary (via) points to shape the route and maintain its integrity in the GPS. Just how many intermediary via points you need will depend on how complex the route is. Generally though, the more secondary roads in the route the more intermediary points you will need.

The New England Riders Basecamp Tutorial can guide you step by step in achieving this.
Learn Garmin Basecamp with New England Riders Tutorial:
https://www.newenglandriders.org/learn-basecamp/
jfheath
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Re: Mileage discrepancies

Post by jfheath »

I agree in part to your last comment [mention]Breezly[/mention] but when the map is first transferred it should be exactly as it was plotted in Basecamp. And I do mean exactly. This is irrespective of profile, preferences and avoidances.

If it is recalculating when imported then it is often due to the maps being different - or as I found out the other day, the map being installed in a different location from the one suggested in Garmin Express. Whatever the cause, this is not correct behaviour and will mean that every route you transfer will be recalculated before you even put the Zumo on the bike. It needs to be sorted to avoid frustration !

However, if the map recalculates when travelling, perhaps because you deviated slightly from the magenta line, it is an extremely good idea to have made sure that the Zumo has no option but to calculate a route that is as close to the original as possible. the Zumo will rarely be able to work out the same route without some help when you create it on the computer.

When Zumo recalculates, it affects only the section of the route to the next plotted routing point. Shaping or Via. BC now makes an important distinction between these two, but the 660 does not recognise what this is. Garmin changed their use of some terms at some point, which is confusing. If in doubt, i call them 'routing points'.

So it is a good idea to have :
  • A number of strategically placed routing points to force calculation along particular roads.
  • Use the same profile name - basecamp transmits this with the route, but i never tested for this when i had my 660
  • Have the same route preferences and avoidances as far as possible
  • Make sure that when you clip the Zumo into the cradke, it doesnt change the profile - which it can do if you alternate between car and bike.
I cannot tell you how the 660 behaves with Basecamp shaping and via points - i just know that there are issues, and Mapsource is recommended by Garmin

If you have autorecalculate turned off, then your route will never change, but neither will it tell you how to get to the next routing point. But as soon as you rejoin the magenta line, the 660 will carry on navigating you in the right direction.

Today, I discovered something really important. I found another way that doesn't work.
CThody
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Joined: 23 Oct 2019 09:07
Great Britain

Re: Mileage discrepancies

Post by CThody »

Good Morning and thank you for your replies. I will have another play today to see what happens. As far as I can see, all settings in the 660 are mirrored in BC. Will look up “Mapsource”.

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