Hi
It's a cool project you have here, i'm looking forward to hear how it goes.
I'm a noob myself, still tinkering with blinking LED's and motors.
I just have a thought regarding the issue logging the data simultaneously.
The question might more be to the guys following the thread with some more experience.
Would it be possible to take a time stamp from the GPS NMEA sentence and stamp the transducer data with it? then you would have a latency from the equipment.
Many GPS systems can output more than one sentence at once (GGA, GGL, ZDA(time and data as i recall), ect.)
I'm sure it will involve some advanced programming if its possible.
Just putting it out there 