IMU calibration

This topic applies only to Trimble receivers which have a built-in IMU sensor.

The IMU sensor in the Trimble receiver continuously determines the orientation and degree of tilt of the receiver. When combined with GNSS the receiver can continuously determine its position and correct for any amount of tilt.

The IMU bias calibration procedure enables the receiver firmware to measure and correct for excessive IMU biases. This affects the fundamental operation of the IMU sensor and so must be performed with utmost care, at approximately the average temperature that the receiver will operate in, and following the on-screen instructions as closely as possible.

Excessive IMU bias can be caused by any of the following:

  • The receiver may have been dropped or suffered from some other form of physical shock.
  • The receiver has experienced a large temperature variation since the last time an IMU bias calibration was carried out, or the temperature is very different (many tens of degrees) from the time of the previous calibration.
  • The internal biases inside the IMU increase as the sensors age over a long period of time.
  1. Remove the radio antenna and quick release from the receiver.
  2. To open the IMU calibration screen, tap and select Calibration. Tap IMU calibration. Read the text on the following screen before tapping Next.

  3. Place the receiver on a very stable surface free of all vibration and any movement (it does not need to be level). Tap Start.

    When the progress bar for the first step has completed, instructions and a picture of the receiver laid on the side appears and the eBubble is shown. For the remaining steps, the eBubble will operate as if the instructions are being followed and the side of the receiver facing upward is to be leveled.

  4. Lay the receiver LEDs down, with the top of the receiver facing toward you. Tap Start before centering the eBubble, and hold still. The progress bar will start when the receiver is leveled appropriately, and will continue as long as the eBubble remains level. If the eBubble goes out of level, the progress suspends until the eBubble is leveled correctly again, then continues from where it was paused.
  5. As the progress bar for each step completes, a new set of instructions and a new guide picture appears. Tap Start at the beginning of each step and follow the instructions very carefully, holding the receiver as still as possible for each step. The receiver automatically starts the process when the receiver is leveled in the correct pose, and automatically progresses to the next step when each step is completed satisfactorily. If the receiver detects a step has already been completed satisfactorily then that step will be skipped in the process.
  6. A confirmation message appears when the process is completed. Tap Done to set the new IMU bias correction in the receiver.