Greyride

Yesterday i went for a long ride.. ( ok, 21 miles for me is like a century for you). The last part of the ride seemed very flat or even down hill. I Down loaded the information and I found something very weird. The last part was an elevation gain ( about 300 ft over 5 miles). So to my eye I was going down hill but I was really going up hill? Is this an error in the Garmin?

10 Wheels

That is called a false flat.

You are pedaling up a grade, but it seems to your eyes that you are going down.

The way to find out is to coast.

This one went on for 26 miles.

Greyride

Yikes!

10 Wheels

Sometimes you can look behind and see that you are really going up.

Looigi

Which Garmin and what did you upload your data too? The Garmin 500, 705 and 800 (and maybe others) use barometric pressure for elevation gain/loss which can have some drift due to ambient pressure changes and sensor drift. Usually sites you upload your data to have an option to correct it for known elevations along your ride. If you click this option, it adjusts the Garmin data to coincide and can improve accuracy.

GeorgeBMac

While I agree with 10 Wheels (that it can be hard to determine visually), another possibility is:

I use Strava on my IPhone and keep getting different elevation readings for the same course: For instance, on an 8.5 mile segment (17 miles round trip), Strava reads anywhere from an 850 foot climb to 1250 feet. It really gets wierd through the two tunnels -- I see climbing spikes in both of them -- Stava may think I am going over the hill rather than under it...

rdtompki

300' over 5 miles is barely over 1% and on a single can be very hard to feel (or see for that matter). The slightest breeze would present a similar resistance. I don't know which Garmin you have, but I've generally found elevation and grade to be accurate.

Greyride

Garmin 500 will check settings. Using Garmin connect. I didnt find any options to adjust elevation changes.
Thanks

cplager

The Garmin Edge 500 uses barometric pressure to measure altitude more accurately than GPS does by itself. So this is much better than units (e.g., Garmin Edge205) that don't.

That being said, this still isn't perfect. If you scroll down and look on the left hand side of a Garmin connect page, you'll see "Elevation correction." For you guys looking at my page, it just says enabled. For me, I can choose enable/disable.

What is supposed to (and often) happen is that this will use the elevation data from the maps it has to provide a more accurate measurement. What sometimes happens (and it very strangely depends on which device I use to upload the track) is that this makes the data worse (has spikes in elevation that are clearly non-physical). I've sent Garmin tracks like this and they pretty much blew me off.

Cheers,
Charles

woodway

The iPhone does not have a barometric altimeter therefore when you upload your track to Strava they use a database of elevations to calculate your elevation gain. The actual elevation points used can differ on each ride. That's also why you see climbing spikes going through the tunnels. Here is the explanation from Strava:

https://strava.zendesk.com/entries/2...elevation-gain

Greyride

Did it and the data got spikyier. So I guess it was correct.. going down hill on an uphill grade.. odd

GeorgeBMac

That all sounds good but, the fact is, I am riding on the same 8 foot wide trail from the same start point to the same end point -- there is no deviation. But Strava continues to show a very wide deviation -- from 850 climb on one ride to 1250 feet on another...

Yes, Strava provides an explanation of how they calculate the climb elevation, but they do not explain how it can change from day to day. But, perhaps the explanation comes from their statement that they "smooth" the numbers... Perhpaps they are doing a little too much smoothing?

But, for the most part, the Strava distance caculations are pretty accurate and are always very close to what my cycle computer shows. And for me, that is what I look at most: the distance...

I also like how it accumulates that distance and can show it day-by-day and month-by-month.

All in all, I like Strava -- but it simply isn't very accurate for elevation.

Esteban58

I've tried 'mapmyride', 'ridewithgps', strava, and garmin connect all with my edge 500... They are all pretty consistent with mileage (when they differ, its by .1 mile and seems to be rounding related). For Altitude, they can be all over the map.

One thing I've just set and will be trying out for the first time today is using an 'Elevation point' - set for the elevation at the end of the courtyard - I've noticed that the starting elevation for
my rides has been pretty inconsistent - perhaps temperature dependent?

GeorgeBMac

I have trouble buying that a 300 foot climb is "very hard to feel"... Basically, it is climbing a 10 story building -- and most people would not find that hard to feel. Actually, most people I know could not do it. Or, if they did, they would be panting at the top.

But I do agree that a headwind can pose a similar resistance.

But, I post this to caution experienced cyclists to be cautious with their words around new cyclists. As a new cyclist I have heard things like "Anybody should be able to do 25 miles..." or that you should not be able to feel a 300 foot climb...

It is misleading -- which could lead somebody to push themselves beyond their abilities and risk, amonst other things, discouragement.

Greyride

I can totally feel a 300 ft climb. I was exhausted at the end of it.. Now after looking at it I kinda wish I had turned around... Down hill is fun!

Rick@OCRR

I agree that both Garmin and Strava can have huge deviations over the same course on different days. I record my commute to and from work numbers for elevation gain and each time I just laugh . . . exactly the same course, but quite a variation in elevation totals. And that's on an 18 mile (round trip) commute.

One of my favorite mountain roads (Glendora Mountain Road) from Glendora to Mt. Baldy Village and back is right at 5,000 total feet of climbing (on average). Some days it's just shy of a mile (5,220 feet), and last weekend it was only 4,815 (over exactly the same course)!

So I would say, take any Garmin elevation numbers with the proverbial grain of salt. Or . . . just consider them to be '"close enough" for your purposes (which is what I do).

Here's my Strava data read from a GMR ride (except that we added the 2,000 foot Ski-Lift climb) awhile back, just FYI.

https://app.strava.com/rides/22979485

Rick / OCRR

rdtompki

I apparently didn't make my point very well - depending upon rider weight and normal cruising speed a 1% grade at the same effort might slow things down a bit over 2 mph. This is certainly significant. What I'm saying is that visually 1% can be very hard to discern and given all the other variables, the greatest being wind velocity and direction, it can be almost impossible to tell whether or not you're climbing just from feel. Now, the Garmin display elevation and as your true elevation increases you will be able to visually observe an increase in altitude/elevation.

The new Garmin 800 has much more lag in it's grade calculation and display, but on the tandem I can tell when 1% is about to display, not so easy on a single.