Difference in ascent/descent figures in Bikely and Mapmyride

johncp

Have just discovered Mapmyride and plotted a 73 mile route. Overall climb is given as 1427 feet and descent as 1425 - pretty good. But the same route mapped using Bikely software comes in at 4131 ascent and 4121 descent! Highest points compare well at just below 1000 feet and the overall profiles correspond pretty well. This is the route http://www.mapmyride.com/ride/united-ki ... 1185337862 or http://www.bikely.com/maps/bike-path/74137

How can there be a 3-fold difference between two sites???!!! I'm inclined to go with the Bikely result simply because I know the area well and know that there is a lot of climbing and descending. Even a ball park figure guesstimated from the profile of the route shows a total climb of well over 2000ft. - but nowhere near the 4131 of Bikely.

Woss goin on?!?!?!?

andrew_s

The Mapmyride FAQ says

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.

Adding in every separate 1m rise makes quite a lot of difference, especially when a fair number of climbs aren't real. Google maps based sites don't hold height figures for every square foot of the world, but more like for every 50m square, and interpolate between centre of square figures to guess a height for the actual location of your route. Thus the reported height will depend in part on how high adjacent ground is.

"Amount of climbing" depends on what you consider a climb, and what's an insignificant bump that you ignore. At one end of the scale you take the bottom and top heights for all the significant climbs you see on a map, and do a bit of basic arithmetic. At the other (impractical) extreme you could add a couple of cm every time your front wheel climbs out of a pothole.

Try doing a contour count on an OS 1:50,000 or 1:25,000 map to get an idea of what a real figure ought to be.

John Stevenson

Google maps doesn't provide elevation data - that comes from a NASA database.

Bikely sums all the differences between waypoints. Since there's some noise in the data, that does tend to exaggerate total gain/loss, especially in rolling country.

Mapmyride ignores smaller differences. Looking at the csv it makes available, Mapmyride doesn't credit you with any climbing until you reach 187fst asl. You started at 87ft asl, but you're only credited with 30ft of climbing. That's clearly a bit too conservative.

We both need better algorithms I think.

mea00csf

I found mapmyride just went totally insane. the high point minus the low point on a ride was more than the total climb, clearly ridiculous!!

I exported the data into excell, which is really easy, and then did a "if height b is greater than height a, = b-a, if height b is less than or equal to height a, =0" type calc and it seemed to work pretty well.

God i'm a geek! :oops:

portuguese mike

Or you could just get an altimeter. my sigma computer has one and i find it really useful even if it isn't 100% accurate.

mea00csf

yep, but that would involve actually riding the route :shock:

Speck

Could it be one is in metres and the other in feet? 3.2808 feet to one metre.

johncp

I just wanted to compare a local route with the Autumn Epic which is coming up soon, to get an idea of what to expect. Since the Autumn Epic route was plotted with MMR and come out with well over 3000 feet climb and my hardish local route came out at 1400 feet I think what I can probably expect is...... oh sh!t! :shock: