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# VNDetectTrajectoriesRequest

A request that detects the trajectories of shapes moving along a parabolic path.

```
class VNDetectTrajectoriesRequest
```

## Overview

After the request detects a trajectory, it produces an observation that contains the shape’s detected points and an equation describing the parabola.

## Topics

### Creating a Request

[`init(frameAnalysisSpacing:trajectoryLength:completionHandler:)`](/documentation/Vision/VNDetectTrajectoriesRequest/init(frameAnalysisSpacing:trajectoryLength:completionHandler:))

Creates a new request to detect trajectories.

### Configuring the Request

[`targetFrameTime`](/documentation/Vision/VNDetectTrajectoriesRequest/targetFrameTime)

The requested target frame time for processing trajectory detection.

[`trajectoryLength`](/documentation/Vision/VNDetectTrajectoriesRequest/trajectoryLength)

The number of points to detect before calculating a trajectory.

[`objectMinimumNormalizedRadius`](/documentation/Vision/VNDetectTrajectoriesRequest/objectMinimumNormalizedRadius)

The minimum radius of the bounding circle of the object to track.

[`objectMaximumNormalizedRadius`](/documentation/Vision/VNDetectTrajectoriesRequest/objectMaximumNormalizedRadius)

The maximum radius of the bounding circle of the object to track.

[`minimumObjectSize`](/documentation/Vision/VNDetectTrajectoriesRequest/minimumObjectSize)

The minimum radius of the tracked shape’s bounding circle.

[`maximumObjectSize`](/documentation/Vision/VNDetectTrajectoriesRequest/maximumObjectSize)

The maximum radius of the tracked shape’s bounding circle.

### Inspecting the Results

[`results`](/documentation/Vision/VNDetectTrajectoriesRequest/results)

The array of detected trajectory observations.

[`VNTrajectoryObservation`](/documentation/Vision/VNTrajectoryObservation)

An observation that describes a detected trajectory.

### Identifying Request Revisions

[`VNDetectTrajectoriesRequestRevision1`](/documentation/Vision/VNDetectTrajectoriesRequestRevision1)

A constant for specifying revision 1 of the trajectories detection request.


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