[Paparazzi-devel] Just an idea on sonar-baro assisted landing.

[Chris]

I just had a flash and i came up with the following idea:
What if we enable the sonar just to get a good reading by applying very 
strong filtering and data analysis ( say the sonar indicates 3m from 
ground) and then apply this reading to the barometer without taking any 
more sonar readings in to account?
The barometer does not produce noise and it is very accurate for the
descent rate and altitude when the altitude variations are small
and within a short time.
Assuming a barometer with 0.5m (worst case) step accuracy then if the 
sonar positively indicates just once that we are 3 meters from ground 
then we can say:
altitude = 3m - ((baro_pressure_when_3m_were indicated - 
present_pressure) * baro_scale)
Any opinions on this approach?
Chris