Name: Sensible Grade
Rating: 4.5 (24 reviews)
Author: flyingflo

This datafield shows useful live road gradient. 
It does this much better than the stock gradient data field,
which seems to rely on GPS data (at least on older devices), which is the worst sensor for the job.

A vertical speed / VAM field is also available.

Details:

- Uses the best available data: barometric altitude, bike speed sensors, GPS as a fallback.
- Adjustable smoothing: fast response vs. smooth values with variable length moving average filter.
- 3s altitude sampling interval to accumulate significant altitude delta.
- FIR filter smoothing. 
