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mtbr dismember
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Discussion Starter · #1 ·
So today I decided to run both my 705 and 800 on the same ride. However, I left the "auto pause" option on the 800. Here is a link that compares the stats side by side. Click on the "more detail" button. The 800 includes temperature. Next time I'll try the same setting for both. But this data begs the question, to use auto pause, or not use auto pause?
 

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since 4/10/2009
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Wow, that had to be some serious drift going on at lap 7 to rack up a whole mile in less than 10min. That right there pretty much amounts to your entire distance error between the two.
 

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mtbr dismember
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Discussion Starter · #3 ·
Slow speed?

NateHawk said:
Wow, that had to be some serious drift going on at lap 7 to rack up a whole mile in less than 10min. That right there pretty much amounts to your entire distance error between the two.
That was a long slow climb and I had to push my bike a few times. Do you think that the auto pause is coming on if it thinks I'm stopped, even though I'm riding very slowly and/or pushing my bike? I think I'm going to turn auto pause off. It certainly is underreporting my mileage. Even if I'm going slow or pushing my bike that mileage counts :D
 

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Double-metric mtb man
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Are you running just the GPS, or do you have the speed/cadence sensor too?

For myself, I noticed there was a hair bit of a difference between my Edge (a 305) and a "regular" bike computer when dealing with the auto-pause (like maybe 250 ft in a 20 mile ride when there were lots of starts and stops), but nothing like that 1 mile.

The biggest thing I find with the GPS's is that they seem to record horizontal distance and let the altimeter do the rest. In hilly terrain, I find that there was more of a difference in what the GPS alone would tell me vs. what a "normal" bike computer did.

I added the Speed/Cadence sensor to my set-up and, although the GPS doesn't always go to the sensor for info, it has seemed to help refine it a bit more.

Of course, this is IME, and YMMV.
 

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Premium Member
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NateHawk said:
If you were not stopped, but moving slowly up a hill, it sounds like auto pause might be doing it. To lose a whole mile out of less than 6 is a bit much.
That sounds likely to me. With my 305 the %grade stops displaying below ~2.5mph.

I use the setting in Ascent (Mac software) to adjust the moving time after downloading.

There is an 800 in my future.
 

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trail rat
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Yes, on my 705 (and 305 prior) the auto pause has a lag of when it stops recording and starts recording; I have the beeps on, so I know when it starts and stops. If I am climbing slow in tree cover and north slopes, it will auto pause. When I have to get off and push, it is especially noticeable that the lag of start can very late compared to my moving on auto stop and start.

I had not really thought about the effects of using auto pause on distance. I have always used it on both units, since I have a Time and Paused Time screens on the display. Sometimes I want to keep moving and it works. Other times, when I ride out to do trail work, I want to know ride time separate from work time.

I'm going to experiment with auto pause off.

Wherewolf, since you have two units, some comparisons with both units auto pause and no auto pause will really shed some light on this, I'm thinking.
 

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since 4/10/2009
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Interesting. The Edge 705 measured exactly the same distance for your 3 laps of the same loop, but the 800 was a little different each time.

HR was pretty much the same AFAICT.

Elevation is quite different. Almost 800ft over 27mi. That's pretty significant. Can you post screenshots of the Topofusion Climbing Analysis for these two rides? I'd like to see how those numbers compare to other elevation measures like the DEM-based data.
 

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mtbr dismember
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Discussion Starter · #12 ·
Topofusion

NateHawk said:
Can you post screenshots of the Topofusion Climbing Analysis for these two rides?.
What does all this mean and how can they be so different? All the stats are considerably different in Topofusion. I would accept about 2,100 ft of climbing there as indicated by the 800. There is no way I could get 3,600 ft. of climbing as indicated by the 705.

 

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since 4/10/2009
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That's interesting. The DEM value should be about the same between the two rides, since both rides are overlaid upon the same DEM data. That tells me there's a positional accuracy difference between the two. Most DEM data that's easily accessible has a 30m resolution, so it's going to lose out on a lot of fine detail elevation changes, but it'll be consistent over the entire ride.

Can you post a screenshot of the two tracks overlaid on each other?

How many track points are contained within each file (also, what's the set recording frequency of each GPS)?

One thing I notice from the 705 is that the elevation drifts slightly downward over the course of the ride. You can see it by comparing your start/finish points (should be the same, of course). The 800 keeps the start/stop pretty close to the same and I don't see any obvious drift.

I would really like to see elevation profiles for at least some of the choices in Topofusion's Climbing Analysis, but I can't figure out how to get more than one plot up (and only for whatever elevation values are recorded in the file).
 

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mtbr dismember
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Discussion Starter · #14 ·
Download

NateHawk said:
Can you post a screenshot of the two tracks overlaid on each other?
How many track points are contained within each file (also, what's the set recording frequency of each GPS)?I would really like to see elevation profiles for at least some of the choices in Topofusion's Climbing Analysis, but I can't figure out how to get more than one plot up (and only for whatever elevation values are recorded in the file).
Download the two files and you can play with them all you like. The 800 has more than twice as many track points as the 705.
 

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trail rat
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Wherewolf said:
Download the two files and you can play with them all you like. The 800 has more than twice as many track points as the 705.
How do you have the 705 set to record tracks? I know it can be set for Smart or One Second recording, and the 800 only has Smart, unless you have a Power Tap paired that allows One Second.

So this implies that the 800 uses a different "Smart" algorithm than the 705. Good information coming from these comparisons. Keep testing. :)
 

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Goats Rule!
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FWIW, I have a similar problem with with my Oregon 450. My Edge 800 and 705 are usually within a few feet of each other but...the Oregon has consistently been giving me 3-4 times the elevation gain the other units give, once five times the gain. It's frustrating, especially since I've tried everything short of sending the 450 to Garmin.
 
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