* Based on code and ideas from the Arducopter team: Randy Mackay, Pat Hickey, Jose Julio, Jani Hirvinen, Andrew Tridgell, Justin Beech, Adam Rivera, Jean-Louis Naudin, Roberto Navoni
* Thanks to: Chris Anderson, Mike Smith, Jordi Munoz, Doug Weibel, James Goppert, Benjamin Pelletier, Robert Lefebvre, Marco Robustini
1) Inertial navigation for X & Y axis (Randy/Leonard/Jonathan)
2) 3D waypoint navigation library (Leonard/Randy)
WPNAV_SPEED, WPNAV_SPEED_UP, WPNAV_SPEED_DN control target speeds during missions and RTL
WP_YAW_BEHAVIOR to allow disabling yaw during missions and RTL
3) PX4 support (some features still not available) (Tridge/Pat/PX4Dev Team)
4) Safety improvements:
Tin-can shaped fence (set FENCE_ENABLED to 1 and copter will RTL if alt > 150m or horizontal distance from home > 300m) (Randy/Tridge/Leonard)
GCS failsafe (set FS_GCS_ENABLED to 1 and if you are using a tablet to fly your copter it will RTL and return control to the radio 3 seconds after losing telemetry) (Randy)
pre-arm checks to ensure accelerometer and radio calibration has been performed before arming (Randy)
5) motor interference compensation for compass (Jonathan/Randy)
6) Circle mode improvements:
set CIRCLE_RADIUS to zero to do panorama shots in circle mode (copter does not move in a circle but instead slowly rotates)
CIRCLE_RATE parameter allows controlling direction and speed of rotation in CIRCLE mode and LOITER_TURNS (can also be adjusted in flight from CH6 knob)
7) SONAR_GAIN parameter add to allow reducing the response to objects sensed by sonar (Randy)
8) support for trapezoidal quads (aka V shaped or FPV quads) (Leonard/Craig)
9) performance improvements to dataflash logging (Tridge)
10) bug-fix to analog read which could cause bad sonar reads when using voltage or current monitor (Tridge)
11) bug-fix to motors going to minimum when throttle is low while switching into Loiter, AUTO, RTL, ALT_HOLD (Jason/Randy)
12) bug-fix for auto disarm sometimes disarming shortly after arming (Jason/SirAlex)