differing altitude on 2 garmins

[Drdaz]

Please can some1 help me, I rode with a mate on Tuesday and did the Same course but got 2 complete different readings in terms of total meters climbed! I would understand if it was 10-15 m difference but my Garmin recorded 840m and his was 1200m. Has any1 had this problem before and how can I sort it out???

 

Much appreciated

 

Daz

[Rudi Pollard]

Was it exactly the same models or two different models? Not all models use the same method to calculate elevation.

 

One of the two units may also need calibration...

[Vinnydabutcher]

One is prob barometric and the other one not

 

Did it get colder during the ride? Or did you ride into a big valley of some kind?

 

Reason for the question is that some units use temp in there calculation that can through it off.

 

We have a friend that does on avg about 400m of climbing more that us on a 1500m alt gain almost every time.

 

It makes his Strava look good!

[IH8MUD]

Is the "vents" for the barometric sensor clean and open?

or

Like Lapa said, probably one unit needs calibration

 

But take into account, this is not precision instruments.

Influenced by temperature and humidity

On different days my Garmin Edge 500 gives different altitude for the same place . . .

Buddy of mine rode into a rainstorm on level road, his Garmin Edge 800 said he climbed 400 meter in 3km!

We are 4 guys, all riding with Garmin Edge 500 units. The is always a difference. Sometimes up to 150 meter on long rides.

[Drdaz]

Was it exactly the same models or two different models? Not all models use the same method to calculate elevation.

 

One of the two units may also need calibration...

 

Where can i take it to get it calibrated???

[Rudi Pollard]

you can do it yourself if you know the right altitude at a specific location...

[Pure Savage]

You can always roll the dice and click altitude correction in Strava, I dont know what it is supposed to do but sometime gives some funny results.

[IH8MUD]

I always "feel/think" (no scientific back-up) the best to calibrate a barometric altimeter is to zero it when sitting/lying on the beach . . . .

 

 

If not possible . . . . Do as lapa said. Get location with know altitude .

[rudi-h]

GPS altitude measurements are very poor. This is an example of a vehicle driving around a circuit. The latitude data is solid and it is very easy to identify the pattern, however there is no order in terms of the altitude data. Same goes for a bike GPS. Altitude is a mere indication and does not have any form of repeatability.

 

[Shebeen]

hard to say what the issues are without looking at the models used.

Altitude on a gps is not straight forward at all.

 

GPS uses positioning from a minimum of 3 satellites to work out where it is in 'space', remember the earth is not a round ball like a globe, but is 'modelled' to an approximation(there are different types of model that can be used too, but let's not get sidetracked).

 

This is quite easy to translate into a decent reading of lat/long using the model, but altitude is much harder to represent at the same accuracy. Barometric pressure is much more accurate, but needs to be calibrated as it uses air pressure. this changes slowly but constantly with the weather patterns passing.

 

A retuning technique like the one mentioned on strava would scrub the alt data away and recalculate using what is on the computers for the route used.