# Module `orientation-estimate`
**Package `com.here.mom.component.orientation-estimate`**
**Parts**
* [OrientationEstimate](orientation-estimate.md#orientation-estimate)
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## OrientationEstimate
part **OrientationEstimate**
**Module** [orientation-estimate](orientation-estimate.md#module-orientation-estimate)
The orientation of an object expressed as a unit quaternion (Hamilton not
JPL) and its covariance. The quaternion represents a rotation between two
coordinate frames.
An example of a rotation between coordinate frames is the rotation between
the (Forward, Left, Up) (FLU) internal coordinate frame of a vehicle and the
(East, North, Up) (ENU) coordinate frame defined at the current position of
the vehicle.
| Property | Type | Modifier | Description |
|---|---|---|---|
| orientation | [HamiltonQuaternion](../hamilton-quaternion/hamilton-quaternion.md#hamilton-quaternion) | | Quaternion representing the rotation. |
| covariance | [Covariance3DMatrix](../covariance3d-matrix/covariance3d-matrix.md#covariance3d-matrix) | | The covariance matrix quantifies the uncertainty of the`orientation` property. The assumption is that the uncertainty issmall and so it is legitimate to go to a simplified, Cartesianspace (aka manifold) and express the covariance as a 3x3 matrix.The details of "lifting" a quaternion to this manifold are inhttps://arxiv.org/pdf/1107.1119.pdf and particularly section 3.6.4defines the operators needed to define the space.This covariance matrix is a unitless quantity. |