Sonar Orientation

Third Party Products Sonar and Acoustics
1

Hi I am mounting the Omniscan 450 side scan sonars back to back under the hull of our unmanned boat.
Dose it matter what orientation they are? (see pics attached) I didnt read anything pertaining to this in the blueBoat guide. Thanks

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2

Hi @andrewjamez,

  • The BlueBoat integration guide has them mounted like your second picture, with both cables going towards the back of the boat, but I suspect that’s purely for cable management reasons

  • From the SonarView docs the transducer orientation is settable in software, relative to the vehicle (or to the electronics module, if no vehicle is detected)

  • The Omniscan 450 has a single transducer (like a Ping Sonar, just shaped differently to create a tall, narrow beam), so flipping the way you’ve shown in your picture should have no significant effect on the output because of the long-axis and short-axis symmetries of the beam shape

  • Any other orientation changes definitely do have an effect though, because they change where the beam is pointing / which area it covers

3

Thanks, We are setting them up the same orientation and angles as the blueboat. I take it that the .jason file that BlueRobotics provide to create the “Dual Omniscan sonar” in the devices list contains all the orientation data for that particular setup?

4

Confirming that either orientation shown in the pictures is fine.

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5

json files are human-readable, so you can open it with a text editor/viewer to see what it includes :slight_smile:

config.json 
{
  "session_plans": [
    {
      "name": "Dual Omniscan 450 SS",
      "devices": [
        {
          "note": "port",
          "product_id": "os450",
          "url": "tcp://192.168.2.92:51200",
          "transducer_deg": -90
        },
        {
          "note": "starboard",
          "product_id": "os450",
          "url": "tcp://192.168.2.93:51200",
          "transducer_deg": 90
        }
      ]
    }
  ]
}

Apparently it only specifies the horizontal orientation, in which case I guess SonarView makes some kind of assumption about the tilt angle for its 3D / depth compensation features, although the displayed range numbers may just be distance from the transducer rather than distance projected onto the assumed horizontal bottom plane (in which case the angle is irrelevant) - hopefully @ljlukis can confirm.

6

Indeed, side scan sonar has no information about the vertical angle, so the range shown in a normal side scan display is “slant range” or as Eliot said “distance from the transducer.” Thus, vertical mounting angle is not specified in the config.json file.

SonarView has another trick in which if the bottom signal is sufficient, it can discern the depth beneath the vessel. With that, and the assumption of a flat bottom, it can render a projection of the sonar image onto the sea floor in the corrected location - assuming a valid depth measure and a flat bottom. To see this click the “Depth Compensation” (or 3D) toggles on SonarView.

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