Servers by jDrones

Advice for a first boat of bathymetric cartography

We are in the process of making our first boat.

Frame for prototype: boogie board
2 TrusterT200
Pixhawk Cube black
Survey GNSS: Comnav T300+ in RTK mode, NMEA GGA, RMC and VTG input to GPS1 connector.
Sonar for prototype PingSonar, but we buy a ECT400.

We have some questions about the parameters to be entered regarding the offsets to be filled in for IMU, GNSS RTK and sonar.
The IMU is behind the center of gravity X=0.193,Y=0 and Z= 0.03. We must enter the offset values IMU to center of gravity or center of gravity to IMU?
The GNSS is just above the center of gravity X=0, Y=0 and Z=0.429 (IMU-GNSS X=0.193, Y=0 and Z=0.399). We must enter the offset values GNSS to center of gravity or GNSS to IMU or vice versa?
Is sonar the same protocol as GNSS?

About the data log, for the POS values (lat,long and alt), it is the position of the boat after the EKF2? At the center of gravity or the Cube?

Do you have advice for EKF2 settings with a GNSS RTK?


I finish my boogie board!

Now, I like setup my GNSS, Sonar and IMU offset, but I’m alway the same question about this:

  1. it’s GNSS to CoG, IMU to CoG and Sonar to CoG
  2. it’s IMU to CoG, GNSS to UMI and Sonar to IMU?

Equip_position.pdf (13.6 KB)
According to my scheme it is necessary to setup:
1- GNSS offset Z : 0.395, IMU offset X: 0.18, Z: 0.04 and Sonar offset X: 0.387, Z: -0.098
2- IMU offset X: 0.18, Z: 0.04, GNSS offset Z: 0.355 and Sonar offset X: 0.207, Z: -0.138
1- GNSS offset Z : -0.395, IMU offset X: -0.18, Z: -0.04 and Sonar offset X: -0.387, Z: +0.098
2- IMU offset X: -0.18, Z: -0.04, GNSS offset Z: -0.355 and Sonar offset X: -0.207, Z: +0.138

Can you help me?

Best Regard


1 Like

Does anyone have an idea? Please.


very nice boat you have setup. I have always done gps from flight controller which on my boogie board boat the COG where the flight controller is and I measure all offsets from that. Sonar offsets to me would be the same measure them from center of FC. I see in your diagram you have your FC setback from the center a bit and it looks like the GPS is at COG. I would think you would then set the offsets for the IMU off the COG and everything else set off the IMU in the FC as that will be what is communicating with those devices. I am just spitballing here so could be very backwards from what it needs to be. I am working on 3d printing some thrusters I found online hopefully cut the cost down to 70 or so, the t200 are awesome but bit spendy!

Thanks Matt.

Can you confirm your idea for setup my offset:

IMU offset X: 0.18, Z: 0.04, GNSS offset X: -0.18, Z: 0.355 and Sonar offset X: 0.207, Z: -0.138

For you it’s good?

Normaly I test end of this week on a lac, but it’s not easy in France to obtain autorisation with Cov19 restriction.

I would have a very similar setup, I will use ECT400 (I already have it), ardusimple for RTK. My boat have two T100, but I will need a little bit more power, so I will buy two T200.
@Matt_C could you point me out to the models you are trying to print? I could try them too!

BTW, good project!


here is the thruster I had found to print instead of buying the t200


I am by no means an expert and those measurements looked good to me. I don’t think having one off a bit is going to adversely affect the boat. I am having an esc issue with my boat cannot seem to get full range out of them.

Do you test it? I found the motors on aliexpress and want to buy two of them, but I’m concern about the design.


I have not had time to put it together have been working on other projects but will let you know when I do.

After some test on lac and river, we modify our boat, and we plan to go to 4 T200 (2 right and 2 left) in 18.5V.
Is it possible to connect the 2 Esc (left for example) to the same SERVO output of the Pixhawk?

Has anyone ever tested it?


Servers by jDrones