You might have noticed that there's a difference in the distance/elevation data while you were recording your activity versus once your activity is saved and the data has synced with our servers. The reason is that GPS data from your phone is noisy. We're able to do moderate filtering within the app during the recording of your activity to keep your data somewhat clean, but a good chunk of data-smoothing and cleanup occurs during sync.
Une fois que votre activité est terminée et que vous choisissez de sauvegarder votre fichier, il sera automatiquement mis en file d'attente et se synchronisera dès que vous aurez une connexion stable. Lors de la synchronisation, nos serveurs web sont capables de lisser les données et de recalculer vos statistiques afin qu'elles soient bien plus précises.
For elevation data changes specifically, the elevation gain will be most accurate once you've actually saved your activity.
Once you save your activity, your map is uploaded to the server, at which point we discard all the lat/long points taken from the locations while you were recording and use our own system to replace those elevation values. We then recalculate the total elevation gain based on those values, which will most often result in a lower number for total elevation gain then while you were recording your activity.