4.6:add hires DroneCan mags

common/source/docs/common-advanced-configuration.rst

@@ -79,6 +79,7 @@ tuning options for the vehicle.
     Limit Cycle Prevention <common-servo-limit-cycle-detection>
     LUA Scripting <common-lua-scripts>
     Magnetic Interference <common-magnetic-interference>
+    Magnetometer GeoPhys Array <common-hires-mag-array>
     MAVLink2 Packet Signing (Security) <common-MAVLink2-signing>
 [site wiki="rover"]
     Motor Thrust Scaling <rover-motor-thrust-scaling>

common/source/docs/common-hires-mag-array.rst

@@ -0,0 +1,23 @@
+.. _common-hires-mag-array:
+
+===========================
+DroneCAN Magnetometer Array
+===========================
+
+ArduPilot can be used to create a multiple magnetomer array using DroneCAN compasses. This could be useful as a suspended device for geophysical surveys or other uses.
+
+An ArduPilot autopilot (used only for the array logging, not for vehicle control) could support many DroneCAN compasses as shown below:
+
+.. image:: ../../../images/mag-array.png
+
+And could be suspended below a vehicle as shown below:
+
+.. image:: ../../../images/suspended-mag-array.png
+
+*image courtesy of* `AerialVision <https://www.aerial-vision.com.au>`__
+
+Each compass would have its raw x/y/z field readings logged by the MAGH message.
+
+This capability is not included by default and would have to be included in a custom build for the autopilot using the `Custom Firmware Build Server <https://custom.ardupilot.org>`__ and enabling the "DroneCAN HiRes compasses for survey logging" option under **Compass**.
+
+The autopilot would need to have :ref:`LOG_DISARMED<LOG_DISARMED>` parameter set to log as soon as power is supplied.