Waypoint altitudes

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Waypoint altitudes should be MSL values.

I would prefer feet as most of the aviation community uses feet (at least in 
the US).

However the current altitude relative to starting location is not very 
intuitive. Google earth can easily supply terrain height for planning purposes.

Original issue reported on code.google.com by logan.gr...@gmail.com on 23 Oct 2010 at 11:37

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Original comment by dewei...@gmail.com on 25 Oct 2010 at 5:41

• Added labels: Milestone-Later

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The advantage of setting altitudes relative to home is that the pressure 
altitude sensor doesn't need to be calibrated at the beginning of flight 
(full-scale pilots set the barometric pressure on their altimeter before 
flying).  We could calibrate it to GPS altitude automatically, but GPS altitude 
on first acquisition may not be very accurate, thus causing problems trying to 
land at an exact altitude MSL.  The other down side is that users would have to 
look up their home ground altitude and manually add their desired altitudes for 
every waypoint when creating a mission manually.  And, the justification for 
making the means of specifying altitude different from general aviation is that 
general aviation doesn't have a 400ft AGL ceiling.  If we switched to MSL 
values, it might make it less likely for a user to notice that he has set a 
waypoint that breaks the 400ft ceiling.

We don't plan on changing meters to feet for the APM internal workings (SI 
units are easier to keep track of), but an external mission planner (like the 
ArdupilotMegaPlanner) could convert altitudes in feet provided by the user to 
altitudes in meters for use by the APM.

Original comment by bjpcalt...@gmail.com on 26 Oct 2010 at 7:33

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Original comment by dewei...@gmail.com on 15 Mar 2011 at 5:23

• Changed state: BehavesCorrectly