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Beatchin' Technology
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Discussion Starter · #1 ·
If you traverse a slope while cycling up it, does the Garmin accurately calculate the slope of the hill? I.e. Some hills are too steep to ride straight up :cryin: and require me to traverse. If you are crossing the slope while traversing, would the Garmin (in Training Center) show a lower slope than if you rode straight up it?
 

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Garmin will calculate the slope you actually ride. If you zig zag to make it up a slope your distance will be further than if you were to ride straight up. slope=rise/run since the rise is the same but zig zagging increases the run, the effective slope is decreased. This is all theory. I am not sure how accurately a Garmin will record that.
 

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I'm slow
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What BCH said, however...I find the slope display option pretty much useless on my 310XT. As BCH said, the slope is determined using the rise/run. The problem with the 310XT is that the elevation uses only a GPS calculation and not a barometric altimeter, which makes its accuracy highly questionable. (This can be corrected post ride by comparing data to known reference values) The 500 and several other versions use a barometric altimeter and are much more accurate. I've tried using the slope feature and it tells me nothing more than what I can guess just by looking at the road. Your results with a different model may be better.
 

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Beatchin' Technology
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Discussion Starter · #4 · (Edited)
One clarification

The slope that I am talking about is that indicated in the Training Center software. Not the slope on the display of the Garmin Edge 305, which has a barometric altimeter. The slopes displayed on the unit are steeper than those indicated on the Training Center software.

For example, I got 22.5% on the Training Center file as the steepest slope on Fiddler's Elbow (Jersey) on Sunday. On the steepest pitch of the road, I had to traverse at 1mph to climb it. It occurred to me that the traversing reduced the pitch that the Garmin was 'reading' because I was covering more horizontal distance to ascend the same vertical feet.
 

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Both previous posters are correct. For best results you will certainly want a Garmin with a barometric altimeter, like an Edge 305, 705 or 500 (and perhaps preferably with the GSC-10 speed/cadence sensor in the case of the 500). However, I still would not expect total accuracy with their grade measurements. In your case the tight back-and-forth switch-backs will probably tend to reduce the distance measured (due to the GPS sampling and averaging) leading to a slightly higher grade than what you actually rode. If you really want your Garmin to measure the actual grade of the hill, then I am afraid that you will have to ride straight up it!

Someone also makes a grade-o-meter device (works like a spirit level) that you can mount to your bike.
 

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We have a few hills around here marked by the DOT with grade percentages for some reason, probably a survey. My edge 305 is usually right on with them.
 
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