Greetings DIYDrones community!

I am planning on launching an autonomous boat this summer. The hull is built and the pixhawk purchased.
I have just finished up 

testing the rover software on my 4WD buggy - since it is the best analogue for a boat. So my understanding the PIDS and telemetry system and other small issues have been ironed out.

Now that I have some time up my sleeve, the next step will be sea trials! Well ok, perhaps pond trails, then lake trials and then sea trials.

A little about the boat and the project.

The boat is designed to be a downwind sailer. Mast mounted in the front with a sail (that's the reason for that big wood stump in the front, to hold the mast). The sail is free to spin 360 degrees and will pull the boat along.

There is a keel mounted in back and weighted with lead shot.

The object of the mission is to sail from the Pacific coast following the wind and currents and eventually arrive at Hawaii.

Now to help (or hinder as the case may be) I will be installing a rudder on the boat. The rudder will steer the boat with the winds to keep it on course.

That much can be plotted in Mission Planner and uploaded to the pixhawk. The missing piece of the puzzle is how to update or course correct during the voyage.

Project RockHawk

Enter Rockblock Iridium modem transceiver. The RockBlock operates on Iridium's Satellite SBD - short burst data network. It can transmit up to 340 bytes and receive 270 bytes. Not alot but enough for position updates and course corrections.

This modem has its own arduino library:  http://arduiniana.org/libraries/iridiumsbd/

and would be the perfect device for remote control of the boat while under way. Since sat time is expensive, the plan is to only update the boat as needed. Position updates will be twice per day.

The only issue is how to get the Rockblock to talk with the Pixhawk. This unfortunately is way above my understanding. So I am looking for help to get the RockHawk project going.

The RockHawk must be able to accept remote waypoint updates while under way as well as use the GPS data from the pixhawk to relay back position updates and other variables.

If you are interested, please let me know.