# Calculating ascent inaccurate

I am referring to the ascent calculations for cycle routes.

Yesterday I cycled 27km on a fairly flat route and according to Strava climbed 163metres. Today I cycled 51km and climbed 276 metres on a longer hillier route. The 100 metres difference didn't make sense so I entered it in to Mapometer which came up with 360 metres. I haven't done a detailed analysis but the Mapometer result makes more sense. This isn't the first time I've doubted the Strava ascent figure. Do you know how accurate it is?

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• Elevation on an activity

Elevation on activity pages will be calculated in one of two ways: cross-referencing the GPS data to a database or by using the barometric data in the original file.

• Device with barometric altimeter:  If the GPS device used to record your activity has a barometric altimeter, Strava will use the elevation data in the original file. We do some smoothing to the data, which includes discarding outliers to reduce noise. The amount of smoothing is less on activities with barometric data than it is for activities without barometric data. If your device has a barometric altimeter, but your elevation is being recalculated, please refer to this FAQ.
• Device without a barometric altimeter and the Strava mobile app: If your activity was recorded with the mobile app or with a GPS device that does not have a barometric altimeter, Strava will recalculate the elevation by comparing the GPS data to an elevation database. We do some smoothing to the data, which includes discarding outliers to reduce noise. The amount of smoothing is more on activities without barometric data than it is for activities with barometric data. The accuracy of this calculation is dependent on your GPS data as well as the accuracy and resolution of the database for that region.

k

• Hi Jason,

there is another thread dealing with the issue:

Why such different elevation corrections? (same route logg 1790m, 2615m, 3468m elev gain)

In fact, wherever I rode, from the westernmost islands of Europe over to Asia: STRAVA always calculated elevations wrongly.

Pity the guys don't attend to the problem, which is well analysed meanwhile.

Charly

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