Copter: autoyaw: correct units returned by look_ahead_yaw

[peterbarker]

there are other methods on the autoyaw object which make it clear that they're working in cd, and others in there that work in degrees. This method doesn't specify cd yet returns in that unit.

Change the method and state variable to store in degrees (as our naming standards suggest)

Tested in SITL by using "Set ROI" to swing the vehicle to a yaw, then using WP_YAW_BEHAVIOR set to 3 to swing back to "look ahead"

[rmackay9]

Thanks @peterbarker for finding this.

Could you add a comment to clarify the units of the variable (in mode.h) and return of the function? So above the look_ahead_yaw() declaration in mode.h and implementation in autoyaw.cpp.

This looks like a bug but I wonder could you ever make it misbehave in SITL? Maybe the bug appears for such a short period of time it cannot be seen?

I think we should probably label this as a bug and backport it.

Thanks again.

[peterbarker]

Could you add a comment to clarify the units of the variable (in mode.h) and return of the function? So above the look_ahead_yaw() declaration in mode.h and implementation in autoyaw.cpp.

I considered adding such comments, but "degrees" seems to be our default return in this object (i.e. other methods in here don't comment when they return degrees, but do comment when they return cdeg. That's actually the whole reason for this PR - it didn't conform to that standard! Now I look at it, roi_yaw needs a similar fix.

I've added some comments anyway.

This looks like a bug but I wonder could you ever make it misbehave in SITL? Maybe the bug appears for such a short period of time it cannot be seen?

No, it's not a technical bug; all callers understood the return value to be cdeg-in-a-float, even 'though the method names and comments didn't indicate it was. I could have renamed it to include cd instead to solve the same problem, but since we already have methods returning degrees I thought I'd change this to be like them instead (that's the way we're supposed to be heading...).

fixed my issues,txs

[tridge]

randy approved