Transmit and Receive Frame IDs

[CaptKrasno]

On many (technically speaking all) multibeams have two different reference frame for transmission and for receive. This probably isn't a big deal for small, factory assembled, units like the Norbit or Kongberg M3. However, larger units have a hull mounted transmit and receive units that can be arbitrarily placed.

As I move into formal multibeam projection geometry I would like to formalize how we treat these associated frames.

I suggest we add 2 new fields to ping_info.

• tx_frame_id
• rx_frame_id

Note: for backwards compatibility and for for small, factory assembled, units these may be the same.

For the header frame_id, I propose simply default to the tx_frame_id (as this is the timestamp associated with the time in the header). We can consider this the "master" frame of the unit for sensor-relative projections. This will make for an easy bag conversion rule too to update old messages.

[CaptKrasno]

@valschmidt and @rolker I would appreciate any input you have on this

[lauralindzey]

Seems fine to me, but also, I don't work with large ship-mounted multibeams.

When you put together a pull request, I'll be happy to test the bag migration rule.

[CaptKrasno]

Ok. I will make a pull request shortly

[lauralindzey]

We discussed this briefly.

@rolker suggested only adding receive frame ID, and require the header to have the transmit frame.