Lately I have been doing my bike rides with a GPS logger, and its elevation recording is extremely erratic and thus unusable. Please see:

<http://gpsloglabs.com/share/d9393bc6c20b8b0debfe26234169be632eb019e0/>

You can see from the altitude contour that it does some measurement, but it is too jerky, and thus my total climb is way too big.

How can I work around this problem? Is there any service that will 'flatten' my trip to an accurate topographical map and correct the altitude data?