APM:Copter 3.01 release notes

ArduCopter 3.0.1 has been released and is now available in the Mission Planner, firmware.diydrones.com, GitHub and the new Downloads Area.
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Warnings:
[ol][li]Compass calibration and reducing interference is far more important than with 2.9.1b[/li]
[li]GPS glitches can cause sudden and aggressive position changes while in loiter mode. You may wish to reduce the Loiter PID P to 0.5 (from 1.0) to reduce aggressiveness (see image below of where this gain can be found in mission planner).[/li]
[li]optical flow is not supported but will be back in the next release (AC-3.0.2 or AC-3.1.0).[/li]
[li]loiter turns does not maintain altitude. This bug will be fixed in AC-3.0.2.[/li]
[li]This release has only been lightly tested on Traditional Helicopters.[/li][/ol]
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Improvements over 2.9.1b include:
[ul][li]Inertial Navigation for Loiter and Auto meaning much more accurate control (Randy,Leonard,JonathanC)[/li]
[li]3D navigation controller follows straight lines in all dimensions between waypoints (Leonard,Randy)[/li]
[li]WPNAV_SPEED, WPNAV_SPEED_UP, WPNAV_SPEED_DN, WPNAV_ACCEL allows configuring speeds and acceleration during missions[/li]
[li]“compassmot” to compensate for interference on compass from the pdb, motors, ESCs and battery. (Randy,JonathanC) (Set-up video here)[/li][/ul]

Safety improvements:
[ul][li]simple Tin Can shaped Geo Fence[/li]
[li]pre-arm checks to ensure all calibration has been performed before arming (can be disabled by setting ARMING_CHECK to zero). (video description here)[/li]
[li]GPS failsafe - switches to LAND if GPS is lost for 5 seconds[/li]
[li]Stability patch improvements to stop rapid climbs in very overpowered or overtuned copters[/li]
[li]Circle mode improvements including “panorama” when CIRCLE_RADIUS set to zero (Randy,Leonard)[/li]
[li]SONAR_GAIN parameter added to allow better tuning of sonar surface tracking[/li]
[li]CH8 auxiliary switch (same features as CH7)[/li]
[li]Works on PX4 (some minor features still not available) (Tridge,PatH)[/li][/ul]

How to upgrade:
[ol][li]Make sure you are using Mission Planner 1.2.59 or newer (get it here)[/li]
[li]Click on the MissionPlanner’s Hardware, Install Firmware screen. The version numbers should appear as “ArduCopter-3.0.1”, then click the appropriate frame icon and it should upgrade as per usual.[/li]
[li]Reduce the Loiter and Alt Hold PIDs if you have modified them from the defaults. The modified PID values for the 3DR frame can be seen in the image below.
Note: Nav parameters have been combined with Loiter so do not be concerned if you can’t find them.
[/li]
[li]Although not directly related to this release, if you purchased an APM prior to March of 2013, update your PPM encoder to the latest firmware (instructions here).[/li]
[li]Try out the new version in stabilize mode first, then alt-hold, then loiter and finally RTL and Auto.[/li][/ol]

Numerous How-To videos are available:
3DR Quad Set-Up Suggestions
AC 3.0 Pre-Arm Checks
AC 3.0 Maiden Flight Checks
AC 3.0 “Live” Compass Calibration
AC 3.0 CompassMot Setup
AC 3.0 Fence

Special Thanks to Marco, DaveC and the large number of testers on the pre-release thread who put their copters at risk during the extended testing period. Some of their videos can be found here, here, here, here, here and here. Thanks also to MichaelO for the MP changes required for this release.