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Old 08-15-10, 04:09 PM   #1
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Aha! or, Map My Ride tells part of the truth

So I decided to try to find out just how steep the worst hill of yesterday's ride was. I went over to Map My Ride, and put in a few miles worth of my course near Galena and Bettertown, MD.

MapMyRide said that the whole thing was between -1% grade to 1% grade -- no hills at all.

That, of course, does not square with my memory of events. So I re-entered a route, focusing on just the hill: down Still Pond Rd/292 to the park on Chesapeake Bay, then turn left and pedal like crazy up Ericsson Ave.

That showed a 17% grade, which is a lot more like what my calves remember.

So be careful: MapMyRide seems to show the average slope, but can gloss over the highlights. I don't know how it picks the points between which to calculate the incline, but it can leave out some important details.
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Old 08-15-10, 04:25 PM   #2
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I agree 100% here. If you do the route 1 mile at a time you get a better idea of actual grade. Over a long ride the little grade scale has about 20 sections so it shows a gross grade, maybe fine on rides with crazy climbs. However, it does truly miss all of the rollers. You can export the elevation data and load it into excel and then if you are a nerd do the calculations and plot them. Then you get a more accurate picture, below is an example i think this section of my ride came up as a 2% climb or so. Not that it is overly impressive but in flat ass eastern mass it is a pretty good climb. It is even better when you are at mile 50+. So it can be a useful tool, but the little plot they give you is useless unless looking at stretches a mile at a time.

So yeah I am a nerd.

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Old 08-15-10, 06:06 PM   #3
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These programs all use SRTM (Shuttle Radar Topography Mission) data which is available on 30 meter (approx. 100 ft.) intervals for the United States. I don't know the accuracy of the data and in some geographic areas the data has been augmented from other sources, but 100 ft. spacing (if used by the mapping program) will capture a fair amount of subtlety in the elevation profile. I don't use Mapmyride much, but the standard elevation plot doesn't represent itself as high fidelity. Ridewithgps allows you to expand the elevation profile and it looks like the data is near 100 ft. geo resolution, but I do take this mapping programs max. grade with a grain of salt due to data errors.

Average grade at 1/2-1 mile intervals is useful because these approach steady state efforts on our tandem; I like to see these grades <10%. Grades over shorter intervals can somewhat be estimated with a mapping program, but the best source is probably someone who's been there done that.
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