# FAQ

#### Q: Does Surveyor integrate its own GNSS system? 

A: Surveyor does not include a GNSS device, but SonarView integrates and logs GNSS data from external devices.

#### Q: What GNSS external devices are supported?

A: With BlueOS based vehicles, SonarView connects via MAVLINK2REST to collect and integrate vehicle position and heading information.

A: GNSS devices with NMEA output are also supported. Please refer to [these ](/c/surveyor-240-16/platform-specific-setup/nmea-position-heading-source.md)instructions for more details.

#### Q: Does Surveyor have an IMU?

A: Surveyor has a built-in IMU for roll and pitch compensation. Heading information is supplied by the vehicle (BlueOS/MAVLINK2REST or NMEA). Surveyor also has a compass which we might support in the future, but we think best to use the vehicle's heading information.

#### Q: Where is the phase center (reference point)

A: The acoustic phase center is determined by the receive elements inside the array module on the front of the unit. Below is a diagram showing the location of the acoustic center of the Surveyor 240.

<figure><img src="/files/QS7TixuVRXYJGdQaoymJ" alt=""><figcaption></figcaption></figure>


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