Introduction - If you have any usage issues, please Google them yourself
To use these functions:
1. Start with a KalmanFilter created by alloc_filter_velocity2d.
2. At fixed intervals, call update_velocity2d with the lat/long.
3. At any time, to get an estimate for the current position,
bearing, or speed, use the functions:
get_lat_long
get_bearing
get_mph