EKF wiki clerafications

I was going through the EKF wiki and need help.
On the Commonly modified parameters it says:

EK2_ALT_SOURCE which sensor to use as the primary altitude source

0 : use barometer (default)
1 : use range finder. This can be used for environments where the barometer data is very noisy and the ground is relatively flat (i.e. indoors where an airconditioner may cause sudden pressure changes). This should not be used if the intention is to perform terrain following. For terrain terrain following see copter and plane specific terrain following instructions).
2 : use GPS. Useful when GPS quality is very good and barometer drift could be a problem. For example if the vehicle will perform long distance missions with altitude changes of >100m.

And on the Navigation Overview and Tuning:


This parameter controls which measurement source is used to determine height during optical flow navigation. Set to 0 to use the barometer or to 1 to use the range finder. If set to 1,the vehicle will attempt to maintain a constant height relative to the terrain, which is the default behaviour during optical flow navigation.

Is this the same parameter? What will happen if I use it without optical flow?
What will happen if the signal from the rangefinder is lost for a few seconds/minutes and comes back?


Yes,“EK2_ALT_SOURCE“ and “EKF_ALT_SORCE” have same function about which sensor used as the primary altitude source ,the only difference i think is that the former means the EK2 working ,the latter means the EKF(or EK1,actually DCM) working.
I suggest you set “EKF_ALT_SOURCE=0”(use barometer ) in condition that without optical flow.