# GNSS eBubble tilt sensor

This topic applies to Trimble receivers with built-in tilt sensors, including inertial measurement unit (IMU) or a magnetometer tilt sensor.

The GNSS eBubble uses the accelerometers in the receiver to provide an electronic representation of the degree of tilt of the receiver.

The GNSS eBubble operates independently of any IMU sensors in the receiver. For receivers that support IMU tilt compensation, the GNSS eBubble appears in the software only when the receiver is operating in GNSS‑only mode.

The GNSS eBubble appears automatically when you are using a:

- Trimble R10 or R12 receiver and Tilt functions are enabled in the survey style.
- Trimble receiver that supports IMU tilt compensation where eBubble functions are enabled in the survey style and the receiver is operating in GNSS-only mode.

If you have previously chosen to hide the GNSS eBubble for the current measurement method, it does not appear automatically. To show or hide the GNSS eBubble:

- In the Measure screen, tap the eBubble softkey.
- To show or hide the eBubble from any screen, press Ctrl + L.
- To move the eBubble window to a new position on the screen, tap and hold on the eBubble and drag to a new position.

To make sure the antenna is level

Use the eBubble to ensure the pole is vertical, still and stable when measuring a point, or that the receiver is within the required tilt tolerance. For example:

The circle on the eBubble vial represents the configured tilt tolerance. Tilt tolerance is defined as the distance on the ground (tilt distance) that the tilt represents given the antenna height:

- A green bubble indicates the receiver is within the defined tilt tolerance and the point can be measured.

- A red bubble indicates the receiver is outside the defined tilt tolerance. Depending on the configured tilt warnings, a warning message may also appear if the eBubble is red. See GNSS eBubble tilt warnings.

  If the antenna is outside the tilt tolerance, adjust the pole angle to be within the tilt tolerance.

  Alternatively, increase the tilt tolerance.

To store a position that is outside the configured tilt tolerance, tap . A warning record is associated with the point.

Configure the Tilt tolerance for each point type in the survey style, or tap options in the Measure screen. See GNSS point options.

For best results, when using the GNSS eBubble make sure that:

- You are looking directly at the receiver LED panel. This is because the GNSS eBubble is aligned to the receiver LED panel.
- The GNSS eBubble is properly calibrated. The accuracy of tilt information used to display the GNSS eBubble and stored with measured points depends on the quality of the eBubble calibration. Using a poorly‑calibrated GNSS eBubble degrades the accuracy of the coordinates measured using the eBubble as a level reference.

GNSS eBubble options

You can configure the sensitivity and responsiveness of the GNSS eBubble in the GNSS eBubble options screen. To view this screen you can:

- Tap in the eBubble window.
- Tap and hold the receiver icon in the status bar to view the Receiver settings screen and then tap eBubble.
- Tap and select Instrument / Tilt sensor options.

If you have more than one tilt sensor connected, you can also tap the GNSS softkey from the eBubble options screen for a different sensor. Changing the eBubble settings for one sensor changes the eBubble settings for all connected tilt sensors.

You can configure the following settings:

Option | Description
--- | ---
eBubble sensitivity | The eBubble moves 2 mm for the specified sensitivity angle. To decrease sensitivity select a large angle.
Tilt tolerance | Defines the maximum radius that the receiver can tilt and be considered in tolerance. The allowable range is 0.001 m to 1.000 m.
eBubble response | Controls the eBubble's responsiveness to movement.
Tilt distance | The tilt distance shown is calculated using the current antenna height.
eBubble calibration status | Current calibration status. To recalibrate the eBubble, tap Calib.
Calibration expires in | The date that the current calibration will expire. The eBubble must then be recalibrated.
Calibration age limit | Displays the time period between calibrations. At the end of the time period the software will prompt you to recalibrate the eBubble. To edit the default value tap the pop‑up arrow.