Converting tracks into routes, do they alter?

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There are several threads and posts in the GPS section where bods suggest that converting a track into a route is a very reliable way to avoid alterations in the direction the route takes over that taken by the track. In short, the perceived wisdom is that the converted route will always be faithful to the original track. I certainly thought that to be true, too.

Yersterday leedude03 asked me to help him check that a reasonably long track A to B across France that he'd created in Garmin Adventures could be opened up by me in BaseCamp and be used by me. In other words, that it would be a reasonably safe way to share holiday roads (there was no off-road parts in Lee's track) to be travelled between Lee and his friends. The result was, I'm happy to say, very reliable.... but....

When I asked BaseCamp to convert Lee's track into a route, it did make some very small changes. Zooming in, I could see that changes were where Lee's track had followed a slight curve in say a D road; my converted route would take the straighter (faster) N road.

I have attached my version of Lee's Garmin Adventures file, so bods can hopefuly see the results for themselves.

https://www.dropbox.com/s/rqesj8rnkyl930y/richard 2 - Checked.GPX?dl=0

Lee's two original tracks are there. One is grey, the other I coloured green, just to make it stand out. The green track I then converted into a magenta route. You should be able to see that the magenta route follows the track pretty well, indeed almost exactly. Occasionally it does deviate, as described. Would these changes ruin a holiday? Probably not, but...

1. If it was vital to Lee's life that he'd ridden exactly down the D roads of his track, he'd have missed some small bits out

2. If Lee had been travelling with some mates, 10-1 says that at least one or more of them would be saying something like, "Mate, me GPS was saying go straight on but you went off on a curve through some villages and then went straight on. This Garmin is well fooked" or something similar.

Of course it would be easy to drag the converted magenta line so that it followed the green track exactly. But that tidying-up process would be unnecessary if track into route conversion resulted in an excact translation, just as people (including me) thought it did.

It would be easy and very possibly correct to guess that the slight variations are simply down to:

1. A slight difference between the Garmin maps used by Lee in his Adventure creation and mine

2. A slight difference between Lee's settings and mine

3. A slight difference in the algorithms used between Lee's version of BaseCamp on his PC and mine on my Mac

As I said, not enough to ruin Lee's holiday or mine had I been riding with him or making use of Lee's shared Garmin Adventures file. But enough for me to want to check that a track has indeed converted exactly into a route before I used it.

=======

Do I think that Garmin Adventures is a good and reasonably safe way to share ideas with friends? From this one experiment, yes I do. This was something that Lee hoped to use it for. Having me experiment with him proved, at least to me (and I hope to Lee, too) that it can and does work reasonably well.

Do I think that Garmin's Adventures software (free inside BaseCsmp) is a potentially powerful add-on which, if used fully and properly, can be a nice way to share or just keep records of trips made? Yes. You can add film clips, pictures, note and all sorts of other stuff into the Garmin Adventures file, potentially making it into a pretty good record - a sort if blog, if you like - of what you did.

Give it a go. As leedude03 and I have proved, you can't break it.
 
Just to add to this post, i would suggest that maybe (unsure as i have not tried it yet) if the adventure was left as a track and then uploaded to a nav, this alteration between the track and route however small may not occur.
I can now confirm having uploaded the track to my nav without converting it to a route, (and to make it interesting, i set my navs preferences to a totally different set up than normal) it follows the garmin adventure track to the letter no matter what my preferences are set to, but and there is always a but, the distance of the track has altered by 0.6 mile, the track on basecamp is 271miles and on the nav its 270.4, and having looked at the two very closely i can not see any differences anywhere so go figure.
 


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