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Garmin Montana Trip Odometer


kb6ooc
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I've taken my Montana 600 on two different mountain hikes now. On each hike I've reset the trip odometer so I can see how far I've hiked as the hike progresses. When the 1st hike ended, my trip odometer said I hiked 13.6 miles. I was expecting it to be about 12 miles. When I got home, I pulled the track log out and trimmed my drive to and from the trailhead so I only had the hike (did all that in MapSource). MapSource said the hike was 12.1 miles (which is more reasonable). So somehow the Montana trip odometer reported the hike as being 1.5 miles longer for some reason. I kinda shrugged it off as a fluke of some sort.

 

I just completed another hike a few days ago. Again, I reset the trip meter before starting the hike. Also, I was camping overnight so I didn't have a drive to the trailhead this time (meaning nothing to trim when I pulled the log into MapSource). At the end of the hike, the Montana said I had hiked 9.9 miles. When I got home a day later, I pulled the archived log and looked at it in MapSource. MapSource says I only hiked 8.3 miles. Last time, the Montana said I hiked 1.5 miles further than the MapSource log said. On this 2nd hike, the Montana says I hiked 1.4 miles more than the MapSource log says.

 

I can't let this one go as a fluke this time around. I was wondering if anyone else has experienced this. I'll probably do a bike ride around a pre-planned area specifically to test this out before I report it to Garmin. I figured a bike ride around city blocks is something I can show Garmin and have them look into it (versus a hike on mountain trails). Anyway, curious if anyone else has noticed anything odd like this.

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I've experienced what you're describing albeit on a smaller scale. What I mean by smaller scale is that I'll hike 2 miles and the trip odometer says 2.6 or something. I haven't done any calculations as far as percentages but I'm always a little over on the trip odometer. I always save my tracklog and read the track distance on my unit.

 

It seems that Garmin just can't release a unit that doesn't have the Tracklog - Trip Odometer descrepancy to start with. It usually gets fixed shortly after people start reporting it.

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I performed a test last night on my hike that may shed some light on this issue.

 

I set the tracklog to TIME record at 1 second intervals. After my hike, the trip odometer read 2.8 miles and my tracklog read 2.8 miles. I then repeated he hike with my tracklog set to Auto - Normal. The results were as I thought, the trip odometer read 2.8 miles and he tracklog read 2.4 miles.

 

If the interval of your tracklog is anything less than 1 second you WILL see the traklog distance as less than the trip odometer. It makes sense because the trip odometer records at one second intervals. Recording at anything less will truncate some details that would otherwise be recorded as mileage.

 

Try setting your tracklog interval to 1 second and compare it with the odometer. Give it a test and report back!

Edited by yogazoo
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I performed a test last night on my hike that may shed some light on this issue.

 

I set the tracklog to TIME record at 1 second intervals. After my hike, the trip odometer read 2.8 miles and my tracklog read 2.8 miles. I then repeated he hike with my tracklog set to Auto - Normal. The results were as I thought, the trip odometer read 2.8 miles and he tracklog read 2.4 miles.

 

If the interval of your tracklog is anything less than 1 second you WILL see the traklog distance as less than the trip odometer. It makes sense because the trip odometer records at one second intervals. Recording at anything less will truncate some details that would otherwise be recorded as mileage.

 

Try setting your tracklog interval to 1 second and compare it with the odometer. Give it a test and report back!

 

Good test, and great idea for that test! Your results seem reasonable. The part I am having problems with, though, is that the tracklog (which is always shows LESS distance than the trip odometer) is actually the more reasonable distance. The trip odometer appears to be erring on the high side, whereas the tracklog (which is probably set to auto, in my case, as I have never changed that setting) reports a lower distance and is more reasonable.

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The hardware gives you an approximate current location with an error of up to 30'. When the software plots a bunch of approximate locations to make a track you get an approximate distance. The position errors cause zig-zagging which adds distance. IMHO I don't think a new wheel will help until GPSs get more accurate positions.

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After submitting this as a bug, I received an email back from the Montana beta team saying:

 

It is normal for the unit to display a slightly longer odometer reading than the track log, if the recording method is not set to 1 point per second. What recording method are you using? The reason is that the auto methods may discard points that don’t add much to the shape of the track, but the might’ve added a little distance.

 

which pretty much agrees with the thoughts above.

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I'll have to dig out my 60CS and bring it on my next hike. I don't remember finishing a hike with the 60CS and thinking the trip odometer was wrong - which is the case with my Montana 600. Since my last hike was 8.3 miles (according to the track log I extracted - and its a reasonable number) and the trip odometer was telling me I hiked 9.9 miles (which I know was way too much), I now know not to trust the trip odometer. That hike resulted in a 17% error between the two methods. That would add up to a LOT of extra miles on a really long hike - or drive.

 

SAMM Clan's reply from Garmin is saying that its normal for the unit to display a slightly longer odometer reading than the track log. 17% doesn't seem very slight. However, if its the norm across all GPS units then I'll live with it and change the odometer field to show me something else. Too bad it can't show the accumulated track log distance - that would be far more useful than the 17% error showing from the odometer - which now seems pretty useless. I'll have my old 60CS and the Montana 600 on the next hike and we'll see how the two Garmin units compare.

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If I like to know today's or the current distance I walked, I go to Track Management and overlay the current track on the map. The little box on top shows the distance.

 

I already figured that the tracklog is a more averaged measurement and as such more accurate. When standing still, or even walking, you can see your position jump left to right occasionaly by quite some distance, due to bad readings of the sats.

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If I like to know today's or the current distance I walked, I go to Track Management and overlay the current track on the map. The little box on top shows the distance.

 

I already figured that the tracklog is a more averaged measurement and as such more accurate. When standing still, or even walking, you can see your position jump left to right occasionaly by quite some distance, due to bad readings of the sats.

 

Yes, I agree that going to Track Management and viewing the current track is the way to go. I wish we could have access to THAT distance as a user-selectable field. Then I could banish the "odometer" field forever and just use the accumulated track log distance instead. Maybe I should suggest THAT option to Garmin.

 

I wonder what the track log does differently to remove all that jumping around? I am still amazed how that amounted to a 17% INCREASE in the distance I walked (an extra 1.6 miles on top of the 8.3 I had walked). That's (roughly) an extra 8,500 feet!

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Yes, I agree that going to Track Management and viewing the current track is the way to go. I wish we could have access to THAT distance as a user-selectable field. Then I could banish the "odometer" field forever and just use the accumulated track log distance instead. Maybe I should suggest THAT option to Garmin.

 

I wonder what the track log does differently to remove all that jumping around? I am still amazed how that amounted to a 17% INCREASE in the distance I walked (an extra 1.6 miles on top of the 8.3 I had walked). That's (roughly) an extra 8,500 feet!

Tracks can be run through a smoothing program. I also have wondered why the don't use smoothing on the fly.
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Two more tests this weekend confirm the tracklog / odometer readings at 1 second inervals match up. One thing I wanted to share is that when you save the tracklog of your trip, the distance calculated will be rounded to the nearest tenth when the tracklog is reviewed on your unit. So say you hike 1.97 miles, the tracklog distance will read as 2.0 miles. When you get back on MapSource or Basecamp it will still read as 2.0 BUT when you pointer on the last log in the elevation profile the true mileage (1.97) is shown. Stange and it's something Garmin might want to address (what's so difficult about rounding to the nearest 100th?) but to my point, tracklogs set at 1 second intervals match precisely with the trip odometer.

Edited by yogazoo
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Thanks for sharing those test results yogazoo. Interesting results on the rounding. I agree that rounding to the nearest 10th seems a bit "sloppy". If the Montana was strictly an automobile unit, that might be fine as mileages would typically be longer. However, with the various outdoor modes, a bit more precision would be nice (and probably trivial for a programmer to do).

 

So are you keeping Montana in the 1-second mode now or are you toggling depending on the activity? Obviously the 1-second mode will fill the track log quickly so "auto" is nice. I guess I can configure it for 1-second logging for "recreational" activities and "auto" for "automobile". On the other hand, if I clear the trip meter in recreational mode, it probably means I am about to start a hike and want accurate numbers. I can probably create a shortcut for that.

 

Thanks!

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@Kb6ooc - I only turn on the 1 second record rate if I'm actually going to save the track for viewing later. For driving around town, I simply use Auto - Normal. The pain is that you can't create a shortcut to switch between track recording intervals so you have to go to the setup page.

 

@John E Cache - The 100th digit seems to be significant enough to include in the Trip Odometer field, why not in the tracklog? It really doesn't make sense to me. So Garmin is going to force me to view the last log on my elevation plot in Basecamp every time to get the true track distance? Even if the errors are too big for the 100th digit to be significant, when you round up or down your making the error ever bigger. Garmin, we get it, consumer handhelds have position error, just give me the true distance in hundredths and let me sort it out. And, in all actuality, it creates more headaches for Garmin because people will continue to wonder why their tracklog is rounded and the trip odometer isn't (i.e. why they don't line up).

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