Highly erroneous elevation data recorded in GPS Track mode - Fitbit Android app.

[tonyfrompetone]

I've searched the database to see if there is any information on this phenomenon, but there isn't that I can see.

So: While cycling around my seaside neighborhood I turn on the GPS Track Exercise mode on the Android app (while wearing my Charge HR Tracker). After my circuit the App has recorded my track, distance and time accurately, however the elevation data is completely erroneous. It is telling me that I have gone down to 43 metres below my starting point, which in itself seems to be recorder wrong. I live about 75m from the sea, in a flat neighborhood, at about 4m above sea level. At no stage did I ride into the sea and dive to 40m.

How does the app and /or the tracker read elevation? I am of the opinion that the GPS Track Exercise function records its data independently to the tracker.

Any ideas please?

[Rich_Laue]

Through a change in air pressure.