# DockAccessory.Observation An observation of the contents of a single video frame. ``` struct Observation ``` ## Overview This object represents an observation about a single video frame, including information about the type of subject, the coordinates of the subject, and the angle of the subject’s face. DockKit generates tracking vectors from this frame information. When performing your own tracking, you provide one or more [`DockAccessory.Observation`](/documentation/DockKit/DockAccessory/Observation) objects to [`track(_:cameraInformation:)`](/documentation/DockKit/DockAccessory/track(_:cameraInformation:)-44mwn). ## Topics ### Creating an observation [`init(identifier: Int, type: DockAccessory.Observation.ObservationType, rect: CGRect, faceYawAngle: Measurement?)`](/documentation/DockKit/DockAccessory/Observation/init(identifier:type:rect:faceYawAngle:)) Creates a new observation. ### Getting properties [`let faceYawAngle: Measurement?`](/documentation/DockKit/DockAccessory/Observation/faceYawAngle) The angle of the face in radians. [`let rect: CGRect`](/documentation/DockKit/DockAccessory/Observation/rect) The coordinates of the subject in the frame. [`let type: DockAccessory.Observation.ObservationType`](/documentation/DockKit/DockAccessory/Observation/type) The type of subject in the frame. [`let identifier: Int`](/documentation/DockKit/DockAccessory/Observation/identifier) A unique identifier representing the subject in the frame. ### Defining types [`enum ObservationType`](/documentation/DockKit/DockAccessory/Observation/ObservationType) The available observation types. ## Relationships ### Conforms To [`Sendable`](/documentation/Swift/Sendable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)