Problem pinning me down?

[Rockster2004]

I upgraded from a 396 to an XT this winter, and after using the XT a few times, I've noticed it forecasting my next turn accurately in terms of the road name, but off on the distance by up to 3 miles. Last night I went for a ride and noticed the display correctly showed me at an intersection, but the turn forecast predicted it as 1.7 miles ahead. Is this common?

[Rockster2004]

Nobody? I observed this again on a ride a couple of evenings ago. It seems it often predicts a turn (the instruction at the top of the screen) as being much further away than it actually is, yet the display of my location on the map seems accurate.

[Mzokk]

I've never encountered that with my XT? Factory reset may cure it if its a glitch in the operating system. Just guessing mind!

[Peobody]

I have never experienced it either. Is it displaying subsequent turn? I have definitely had my XT not identify a turn as a turn (no navigational instruction about the turn), almost like it thinks the left was straight ahead.

[FrankB]

I'm suspecting the map material.

- No up to date map.
- Multiple (routable) maps enabled for the area .
- Route created with a different map than active on the Zumo.
- etc.

Update your device, and maps if applicable.
Start by enabling only the City Navigator map (the one that comes with your device) in 'My Maps'.
Dont set avoidances, only 'unpaved'
Recalculate the route on the Zumo. By switching to 'straight lines' and then back to 'faster'.

Good luck

[Rockster2004]

Why would I avoid unpaved? I love a good dirt road! I understand setting my Zumo to match Basecamp, I thought I had them in sync, as I recall there is a setting in Express to update them together? At any rate, I did have 2023.2 on BC and 2022.something or other on XT, but both are 2024.1 now. It's like we went back to the future or something. But seriously, when we're talking about roads that haven't changed in over 100 years and both versions are current to the last year or so, why would there be a discrepancy?

[FrankB]

Why would I avoid unpaved? I love a good dirt road!

If that's what you like. Fine.
The avoidances you set in Basecamp are not transferred to the XT. So to me it makes no sense using them, with one exception 'Unpaved'. If you set that in BC and on the XT it seems to work. But of course that doesn't mean you have to avoid it.

But seriously, when we're talking about roads that haven't changed in over 100 years and both versions are current to the last year or so, why would there be a discrepancy?

Every route in BC has references to the map for which it was calculated. It may not be obvious when you look at the GPX file, but it is there in the <subclass> field. The hexadecimal number 0600FEA4D601110F1200211600000C001500 in the sample contains the Map Segment number. If you install a new map in BC and recalculate, this number is changed to point to the new map segment number. If the route in your XT no longer matches the installed map, you need to recalculate it. For the XT to operate correctly, the Subclass field should be valid!

Sample GPX.
<gpxx:rpt lat="51.597544346004725" lon="5.669084032997489">
<gpxx:Subclass>0600FEA4D601110F1200211600000C001500</gpxx:Subclass>
</gpxx:rpt>

FEA4D601 => 01 D6 A4 FE => 30844158 is the map segment nbr '30844158: NIJMEGEN, NEDERLAND' belonging to City Navigator Europe NTU 2024.1.
See the screenshots made with Javawa GMTK, they will confirm that.

Long story short: Always recalculate your routes after you installed a new map. The roads may not have changed, but the map segment numbers will.
If I have an existing route that I want to reuse I recalculate it in BC and send it again to the XT, as a precaution.

[Rockster2004]

If mapping references are embedded in the GPX file, how is the level of file sharing occurring nowadays possible? People are using vastly different apps to create the files, and they can't be counting on everyone to be running the same exact map releases they created them with.

[Peobody]

If mapping references are embedded in the GPX file, how is the level of file sharing occurring nowadays possible? People are using vastly different apps to create the files, and they can't be counting on everyone to be running the same exact map releases they created them with.

File sharing remains problematic due to the varying calculation of each device. A fellow that I routinely ride with has the same map on his Nav VI as I have on my XT, and we have the same map in BaseCamp, yet we often end up with different routes from a shared .gpx file. The important thing is to try include enough route points to force each device to calculate along the intended roads. It is a challenge that I don't believe anyone can ever master it because we can't always out-think what a device may produce.

[FrankB]

If mapping references are embedded in the GPX file

As far as I know only 2 programs are able to calculate the <subclass>. Basecamp and Mapsource. If you use a program like MRA, Calimoto, Kurviger or Explore, or whatever there will be no subclass in the GPX, or at best the special value '000000ffffff'. Upon importing such a GPX in the XT, it will recalculate it.
I think you have a case where a route already existed on the XT, and then you installed a new map. (just guessing)

how is the level of file sharing occurring nowadays possible?

People find all kind of workarounds.
- Recalculate the GPX they receive first in BC and then send it to the XT.
- Share tracks instead of Routes. Once the track is loaded in the XT, you create a 'Trip from a track' resulting in a recalculation. If I share a route to a TomTom user, I always give them the track, not the route. Works best for them.
- Other ways, that I'm unaware of.
- Live with the error.