Percentage of grade - gotta love these hills!

[maillotpois]

Well, I can comment on elevation gain on mapmyride verses Garmin. Dh just did a ride yesterday that mapmyride said would be 3,500 feet of climbing and his Garmin said it was over 6,000. Almost double.

My Garmin registers "elevation change" and "climbing"...I would expect one to be double the other with the same start/finish point. Is that the possible explanation? Did he use the smoothing software as he uploaded it?

My other question would be: which Garmin? Is there barometric correction? Was it run through Garmin training center or just pulled from the unit itself?

Ok, that's 3 questions.

[salsabike]

My other question would be: which Garmin? Is there barometric correction? Was it run through Garmin training center or just pulled from the unit itself?

Ok, that's 3 questions.

Right---on my Forerunner, there is no barometric correction and I get ridiculous climbing figures--have to run it through Sportstracks to get it fixed. My husband's Edge (705) DOES have that correction and usually gets it right.

[RolliePollie]

This is interesting...thanks, mudmucker, for the USGS info. I did notice that Map My Ride comes up with different results based on whether you make lots of points/clicks on the way up the hill versus just clicking at the bottom of the hill and again the top of the hill (I hope that made sense).

I do have a lot of difficulty with the hill that's supposedly 20%. My front tire is trying to come up off the ground and I'm going under 4 mph, but I don't stand up to pedal (because I can't do it...don't know why...that's another thread altogether). So based on how challenging it is and the info about USGS mapping, maybe it really is 20%!

[Jen72]

This may be a dumb question but how do you find out the percentage of grade on a hill through Map My Ride? I've been riding a few hills to work on my climbing skills and to get stronger and would like to know the grade of the hills. Is there another site I can use to find this kind of information out?

[mudmucker]

This is interesting...thanks, mudmucker, for the USGS info. I did notice that Map My Ride comes up with different results based on whether you make lots of points/clicks on the way up the hill versus just clicking at the bottom of the hill and again the top of the hill (I hope that made sense).

Actually I was just speaking of USGS data in as general terms sort of answering Mr. Silver too, since he mentioned using his county GIS data. Plus my head was in geek mode. I found and read the FAQ on the site later. And, different web mapping sites probably use different algorithms and treat the data differently. Here is a piece in the help section for mapmyride:

We report ascent and descent stats for routes when they become 'significant'. This is currently set at about 60 meters of total climb. We can't guarantee a great deal of accuracy for routes with ascents < 60m, so we don't want to confuse our users by displaying inaccurate data. For long ascents, you should see your stats appear the the right of the elevation profile.

Our ascent and descent calculation algorithms don't count every small elevation change at every point because we need to filter out 'noise' in the underlying data. Prior to our latest algorithm change, we were reporting ascents that were in many cases too high. Our new algorithm gives more reasonable results for a wider variety of routes. However, since we know that this isn't 'perfect' quite yet, we've provided the raw data in CSV format so that users such as yourself can interpret the data as you choose.

Take that with a grain of salt. I am assuming you are doing rise over run or using the percentage readout over the elevation profile info (to answer the previous post) to assess grade. So there is another level of inaccuracy based on the way mapmyride uses the elevation data.

Whatever, if your front wheel wants to come off the ground, then you are on a mighty steep hill.

[OakLeaf]

Mapmyride uses contour lines that are spaced pretty far apart. I want to say 50 ft or maybe even 100. In country like mine, with a lot of short steep hills, my Garmin registers about triple the climbing that mapmyride projects... and there are a lot of local riders who swear that Garmins underestimate climbing by about 10% compared to careful measures on specific hills.