Strava/Bryton 20 Elevation Reading

dinyull

I recently bought a Bryton Rider 20 and signed up to strava.

Been logging all of my rides and when I've been comparing them with a mates I'm noticing that the elevation on similar/identical rides is quite different. Up to 1,000ft different!

What's likely yo be more accurate, the reading I'm getting on the Bryton or the reading from friends iPhone app?

I'm not bothered about not having as much elevation as my mates, I'd just like to know the info I have is correct so I know where I am.

timothyw

Neither of them are likely to have particularly accurate elevation. Strava should probably be correcting the elevation for you - when you look at your ride, underneath the elevation value it should say 'Elevation (?)' - click that and you can tell it to correct your elevation data.

If it won't let you, it has probably already corrected your data, so it should be fairly accurate.

Also, your friends will need to correct their own ride elevation data, I don't think you can.

Bobbinogs

Strava will use its own elevation data by default unless you have a trusted device in which case the Correct elevation feature will use your device's recorded elevation stats (which are always uploaded but not used). I don't think the Bryton 20 is a trusted device though so I suspect the 'Correct elevation' feature won't work.

The most accurate way to track elevation is to set a known elevation point (various websites will let you find this out) and then switch on your GPS unit prior to riding and let it adjust and find the elevation point. Then, overrule the Strava GPS mapped data by using Correct Elevation on each ride. Works very well but only when riding from certain points that have been preset.

Here is some interesting text from Strava:

A barometric altimeter best measures relative elevation changes based on atmospheric pressure. Since changes in atmosphere pressure are very small, and changes are gradual, the resulting dataset will be well "smoothed". Also, the changes in elevation relative to each other will be accurate, but the absolute readings from your Garmin, for example, may not read the exact elevation at that location.

An elevation database created by surveying the land surface will essentially divide the whole world into a grid of squares, with each square reading one value for the average elevation measured in that area. When we use this database to calculate your elevation, we see which "square" each of your GPS coordinates falls into, and use that as the elevation value. A few problems - for much of the world, the dataset is divided into squares measuring 30 meters on each side. For locations with complex topography, a lot can change from one square to another, and the average value of one square might only paint a limited picture of the elevation changes in that square. Pair that with GPS accuracy, and you may have a decent amount of recorded GPS coordinates that place you in a "square" that you were not actually in. Thirdly, this resulting elevation dataset for your activity may not be very smooth, and may have large changes in elevation from one point to another. This can cause issues with inflated elevation readings.

Also keep in mind that when you recording with two devices, you're generating two different GPS files, and each GPS will record different coordinates even if they traveled the same route. GPS is a bit of a whacky technology, and has an average of + or - 50 feet accuracy pretty much at all times. So, if you take two different recordings, and correct them both using the elevation database, you will get two different values (also recording intervals play in here, and a Garmin has a variable recording interval while the mobile app is recording every 1-2 seconds).

What I'm attempting to accomplish here is to paint a more detailed picture of the factors behind the scenes with your elevation correction, and try to explain some of the subtleties of elevation data, and why there can be some variation based on each GPS recording, device, and method of data collection used.

dinyull

I've just chosen the checked the 'Elevation ?' and has changed my ride a little, but not much so would seem my data is pretty close.

I had also noticed bikehike routes were differing in info from my strava rides.

Not fussed about correcting my mates, I had just noticed a sizeable difference in the same route. I just want to be sure that my info is correct so in the future when I plan to go Col hunting in the alps I know my training isn't way off.

motogull

I've got a 200. My mate has an 800. We do the same rides together. He always gets more elevation.

alphacharlie

My 40 lets me store 5 different location altitudes, I use location 1 as my home height above sea level and calibrate to it, if you ride from different start points you can save the other locations and calibrate when at them prior to the ride.
Not sure if your 20 does that too but may be worth a try
Cheers
AC