What is Shim and how do I compensate for it?

Shim occurs when the camera’s mounting platform is not level. On fixed installations the mount is usually level; Shim occurs more frequently on movable platforms such as trailers.

Shim is shown in the figure below, when the camera rotates through 360° the angle of the camera with respect to the horizontal will change. The Camera Manager can compensate for this behavior by adjusting the tilt angle bias for each azimuth position.

Shim Diagram

The Camera Manager requires two parameters the Shim Bearing and the Shim Amount (Note these parameters are found in the Camera Configuration Panel of the Camera Control Client as shown in the figure below).

The Shim Bearing is the bearing angle where the camera is tilted highest in elevation with respect to the horizontal. By rotating the camera through 360° and focusing on the horizon, one should be able to determine this bearing angle.

The Shim Amount is the degrees in elevation the camera is tilted with respect to the horizontal. To determine the Shim Amount, set the camera’s bearing to the Shim Bearing and adjust the camera’s tilt so that the horizon is in the center of the screen. Rotate the camera 180° and readjust the tilt so that the horizon is again in the center of the screen. Take the delta of the two tilt angles and divide this in half, the result is the Shim Amount.

Enter these parameters in the Camera Configuration Panel and click Apply. The camera should now rotate through 360° without any apparent changes to the camera image’s tilt angle.

Camera Control Client and Config Panel