Garmin Edge 305 Question

[Mr. Bloom]

Thanks SB - I knew I had seen it before...right before my eyes

Here's mine from the Hilly Hundred

Ascent Grade Max 18.7
Descent Grade Max -16.8

[SouthernBelle]

Thanks SB - I knew I had seen it before...right before my eyes

Here's mine from the Hilly Hundred

Ascent Grade Max 18.7
Descent Grade Max -16.8

Maybe you should keep that triple!

[Tater]

You people are rotten! Rotten, I tell you!! I have been doing some looking around for a new bike computer, I love my wireless Cateye, but wanted something more. Did some research into the Garmin 305 and ended up picked one up last night. It so appeals to the numbers geek in me! I had a blast with it on this morning's ride.

So thanks for helping me spend some money. But hey, its for the bike, so its all good!

[OakLeaf]

If you're looking for more junk to hang off your handlebars, the Adventure Cycling catalog has a simple bubble level that displays grade in real time. It's bound to be way more accurate than any of the electronic gizmos, whether they use a barometric pressure altimeter or simply rely on GPS data. They're notoriously inaccurate on altitude, although once you import the data into your computer, some of the software will correct the altitude readings against known points on your route.

I have to say, the new Edge models are very tempting. It would be really cool to have access to road maps like we do on the motorized-vehicle GPS units.

[kelownagirl]

DH and I both have Garmins and our data is remarkably similar when we ride together. (Well, except that he goes faster. We upload to Motionbased and find the elevations and grade info pretty darn accurate. We ride the same routes a lot and the info is usually the same every time.

[easterbird]

have you noticed that the grade showing on the edge as you ride is very different from what uploads? 22% becomes 16%. 20-22 was probably closer because all other 16% I can ride but could NOT on that one!

What about difference in HR? On the edge before upload, it reads 140(I was pushing like crazy the whole way and I am almost 60). Upload shows 130. This happens often. Does anyone know why? What about MB gravity? Do you use it? I stopped applying it because it adds about 200-500' depending on ride.

[Thorn]

I don't use the correction for elevation. As discussed somewhere around here, the elevation is relative to the unit doing the recording. So I just use what I get inside of training center and use it.

As for the "instantaneous % grade", it is just that. The GPS in the Garmin is not good for vertical resolution so it also uses barometric pressure. But...every measurement that the GPS takes has a range of error. E.g., a good satellite lock is still +/- 18m or so.

So those instantaneous grades...I look at it this way....when I read out the % grade it is calculated based on the last two data points (ok, not quite the last two, but....). Either of those data points could be in error. When I'm looking at % grades, then, I tend to perform rolling averages in my head. Did the GPS hold the 20% or was it followed by a 3%?

Of course, once imported, it does get smoothed out, even if you turn smoothing off. I have one hill that reads in TC as 10%. It is very short and very steep--trust me, that bump is not just 10%--10% does not require standing in my lowest gear. In the end it is all relative and the resolution of the PC isn't the same as land. Those sharp bumps can just disappear.