I’m interested to know if it is possible to integrate an echosounder with the RS3, such that the output from the echosounder is used as the antenna height of the RS3, so that the final coordinates calculated by the RS3 are actually the varying, virtual antenna height.
The IMU in the RS3 makes this a perfect receiver for attaching to a range finder or sounder which then feeds the offsets into the RS3 and the RS3 records the real-time coordinates of whatever the sounder/rangefinder are measuring.
This would be a fantastic feature, and I can’t find how/where to integrate this via hardware configuration.
@geohawk , I’m pretty sure the RS232 port only outputs data. In this case, I think its the position in LLH.
It sounds like you would need to have a device in the middle to take both the position and depth information to then merge together. If you know the true “sounder” height (plumb between the Reach and the Sounder), you would then just have this device subtract the depth the Sounder reports at the same time each device reports.
I’d think Reach would report its position each second, but you might record say every 10 seconds with the sounder. So your device would just need to synchronise this a bit and spit out what you need accordingly.
Something to consider though is the orientation of the Sounder. When you ride up or down a wave, does it always report the plumb depth, or does the, lets say Beam, tilt with the ship?
Hope this helps, or gives you an idea of how you could implement this?
Unfortunately, the position is projected by the GNSS system to the end of it’s known rod height, which means that the offset coming from the sounder would be projected straight ‘down’ from the bottom of the rod, creating an angular offset, instead of straight along the rod’s axis (as you pointed out).
Any simple single beam is usually not accompanied by an INS which would account for for the motion. If an INS is involved, one might as well go full multi-beam.
Of course, something like a pixhawk or similar could be employed to do the dirty work, but this defeats the KISS method.
This is why it would be optimum to have the ability to ‘feed in’ the “antenna heights”, as the GNSS is doing the angular correction based on its internal IMU.
Of course, at depths of 20m the error will be quite large, but typically, this isn’t too critical for single beam applications (roughly 20cm of error, according to the specs of the RS3, propagated out to 20m).
If your goal is to do mux the data with absolute minimum hardware (RS3 + sounder), I may be able to assist if you contact me directly (not free); but as you mentioned, you can get it done more easily and conventionally with a third piece of hardware.
Then you also have to decide what to do (or what not to do) if the IMU decides is needs more movement for calibration.
