Then I get my static heading, and subtract to calculated bearing. Is that right
Depending on your control method for the base, you might not require a compass. Compasses can be inaccurate if they are too close to magnetic interference.
I use a stepper motor to turn a platform and "count" the steps in order to know my position at any one time. From here, any "bearing" is converted into step positions on a 360 degree base.
The disadvantage to this, is that I don't know my starting location - it's always a step count of 0. So I have a switch on the base that registers "North" for my azimuth (turn table) by turning my azimuth until it receives a switch press. The platform is locked in place so the switch is always facing north. If your base is also moving then you'll definitely require some form of compass...
You can further improve the accuracy of this method by adding an encoder to your motor.
Good luck!