Garmin v Bryton accuracy

Wobblehead

Hi All

Went out today, I've a Gamin 500, mate has a Bryrton of some description..

Mileage recorded by both devices were believable, I did 4100ft ascent,he did 2600ft ascent, lazy git....

Admittedly, i went back down the hills twice for a third rider, but doubt it was that much ascent / descent.

How can they be so far out?

sungod

that garmin has a barometric altimeter, not all models of bryton do

if the bryton is a model that hasn't got one, it'll be relying on gps only

gps devices are notoriously bad when it comes to altitude accuracy

Gizmodo

Taken from the Garmin v Strava Climbing Accuracy thread

This is taken from the Garmin Edge forum (https://forums.garmin.com/showthread.php?t=16046)

Which is more accurate [Garmin Connect Websit or Garmin Edge 800]? That is a good question. Regardless of the device or method used it is important to realize these devices are consumer grade and can introduce a level of error that is not acceptable for survey level data. The Edge 800 is more likely to have more accurate elevation information than the Edge 705 so elevation corrections should be minor.

Are the "elevation corrections" more accurate than the Edge 800? Using the auto-calibration feature on the device, the accuracy is +/- 50-125ft (same as GPS elevation). With WAAS and good reception you can obtain an accuracy of +/- 25-50ft. When manually calibrating to a known elevation it is approximately +/- 10ft for the first 15 minutes. Accuracy can change due to natural pressure changes (changes in weather). Potentially the information on our website may be more accurate as many things can effect the altimeter of your GPS. There is a limit however to this potential accuracy, as indicated on our website, "Elevation Corrections has known limitations for certain geographic features such as bridges and cross country borders where different elevation datasets prevail."

So in summary, in certain circumstances the Edge 800 will be more accurate than Elevation Corrections (and usually more accurate than the Edge 705), but overall the Elevation Corrections may provide the additional accuracy you need. Regardless of your choice, please be aware these devices are consumer grade and only survey grade devices should be used if sub-meter accuracy is desired.

This is what the Strava web sit has to say (https://strava.zendesk.com/entries/20965883-elevation-for-your-activity)

Elevation data recorded by a device can come from one of two sources: either a barometric altimeter on the device (such as those on devices like the Garmin Edge 500 and Forerunner 910XT) or derived from GPS signals (on most other devices, such as the Garmin Edge 200, other Forerunner models, the iPhone, and Android devices).

Strava detects devices with barometric altimeters and recognizes the data from that source. Since elevation data derived from a GPS signal is fairly inaccurate, Strava automatically corrects elevation derived from a GPS source by consulting elevation databases to determine the elevation at each point in the activity. 

If you suspect that your elevation data is incorrect, you can request an elevation lookup.  Click on the "Elevation" text under the elevation statistic above the map. The dialogue pops up with a button to "Correct Elevation". This button will only appear for data collected with a Barometric Altimeter, or if a previous automatic elevation correction has failed. After a short while, the "Calculating" text will change to "Updated", and if you click on "Updated" your page will refresh with the new elevation data. 

Wobblehead

Gizmodo wrote:

Taken from the Garmin v Strava Climbing Accuracy thread

This is taken from the Garmin Edge forum (https://forums.garmin.com/showthread.php?t=16046)

Which is more accurate [Garmin Connect Websit or Garmin Edge 800]? That is a good question. Regardless of the device or method used it is important to realize these devices are consumer grade and can introduce a level of error that is not acceptable for survey level data. The Edge 800 is more likely to have more accurate elevation information than the Edge 705 so elevation corrections should be minor.

Are the "elevation corrections" more accurate than the Edge 800? Using the auto-calibration feature on the device, the accuracy is +/- 50-125ft (same as GPS elevation). With WAAS and good reception you can obtain an accuracy of +/- 25-50ft. When manually calibrating to a known elevation it is approximately +/- 10ft for the first 15 minutes. Accuracy can change due to natural pressure changes (changes in weather). Potentially the information on our website may be more accurate as many things can effect the altimeter of your GPS. There is a limit however to this potential accuracy, as indicated on our website, "Elevation Corrections has known limitations for certain geographic features such as bridges and cross country borders where different elevation datasets prevail."

So in summary, in certain circumstances the Edge 800 will be more accurate than Elevation Corrections (and usually more accurate than the Edge 705), but overall the Elevation Corrections may provide the additional accuracy you need. Regardless of your choice, please be aware these devices are consumer grade and only survey grade devices should be used if sub-meter accuracy is desired.

This is what the Strava web sit has to say (https://strava.zendesk.com/entries/20965883-elevation-for-your-activity)

Elevation data recorded by a device can come from one of two sources: either a barometric altimeter on the device (such as those on devices like the Garmin Edge 500 and Forerunner 910XT) or derived from GPS signals (on most other devices, such as the Garmin Edge 200, other Forerunner models, the iPhone, and Android devices).

Strava detects devices with barometric altimeters and recognizes the data from that source. Since elevation data derived from a GPS signal is fairly inaccurate, Strava automatically corrects elevation derived from a GPS source by consulting elevation databases to determine the elevation at each point in the activity. 

If you suspect that your elevation data is incorrect, you can request an elevation lookup.  Click on the "Elevation" text under the elevation statistic above the map. The dialogue pops up with a button to "Correct Elevation". This button will only appear for data collected with a Barometric Altimeter, or if a previous automatic elevation correction has failed. After a short while, the "Calculating" text will change to "Updated", and if you click on "Updated" your page will refresh with the new elevation data. 

Done this and it has knocked 1100ft off. Reading the above, shouldn't my 500 be more accurate than GPS, or have I got a setting wrong on my garmin?

Gizmodo

Wobblehead wrote:

Done this and it has knocked 1100ft off. Reading the above, shouldn't my 500 be more accurate than GPS, or have I got a setting wrong on my garmin?

As it says on the Garmin forum that I posted above "...it is important to realize these devices are consumer grade and can introduce a level of error..." To give you an example, I've gone into a cafe with my Garmin on pause during a ride and when I come out suddenly I have a vertical descent on my graph. Barrometric pressure for altitude is only reliable if the weather conditions don't change at all during the ride.

Whichever system you believe, Bryton, Garmin, Strava etc. there are inacuracies in all of them - there is no system that gurantees accurate altitude measurements.

rolf_f

I take the GPS unit estimate with a pinch of salt. It's much better to rely on the value given for a route as plotted on the website. That will determine the elevation total for a route based on the elevation of the tiles in the digital terrain map. It will always be prone to slight underestimate, and theoretically never overestimate but, more importantly, it is aways the same for a specific route and consistent between routes.

Diamant49

I cannot comment on a comparison, but clearly there can be problems if a barometric device is not calibrated (or just faulty?). I was looking at the record for the guy on the top of this leaderboard and realised that the max. elevation for this segment was only c. 250 feet (which is what the OS map shows) and his was c. 500 feet. Looked at some of his other segments and it has him at 150 feet when he is virtually at sea-level. He is using a Garmin 800.......

http://app.strava.com/segments/1060437