To enable you to review the data you captured in your movement trials (see Capture movement trials), Vicon Nexus offers a number of tools. You can use the time bar to manually scrub through the trial, or to assess your trials quickly and easily, you can use the automated data quality features of Nexus.

For more information, see:

Review trial data on the Data Management tab

You can quickly obtain feedback on the data quality of all your trials on the Data Management tab.

Note
To display quality information:

If your trials were captured in versions of Nexus earlier than Nexus 2.9, save the trial in Nexus 2.9 or later (eg, by running the Save Trial - C3D + VSK pipeline operation, found in the File Export pipeline operations).
If your trials include multiple subjects, select a single subject only.

On the default Data Management tab, the Quality column displays data quality information about each trial.

The information displayed (from left to right in the Quality column) is:

Number of unused markers
Number of gaps in this trial.
Percentage of markers in this trial that are labeled.

If you are using a custom scheme for the Data Management tab, to display a Quality column, you can either revert to the default layout or, to add a Quality column to your custom scheme:

Right-click on a column and then click Insert column of type and select Quality.

Review trial data using the time bar

To review trial data using the time bar:

Display reconstructed and labeled markers in either of the following ways:
- Ensure that a trial you have just captured has been reconstructed and labeled.
- From the Data Management tab, open a previously captured and labeled trial.
In the Resources pane, ensure Nexus is in Offline mode.
Display a 3D Perspective view and optionally a Graph view.
Tip: To automatically display both views, in the View Type list on the Nexus toolbar, select Data Correction. Using a split layout with both a 3D Perspective and a Graph view enables you to display the results of your editing actions and to select specific trajectories, frame ranges, and gaps in trajectories. Since the graphs indicate what changes have been made to the data and by which tool, you can immediately see the results of any edits you have made and determine if you want to change it again or adjust the data, using a different tool in the Gap Filling section.
Play back the desired portion of the trial:
- Full trial: In the controls at the left end of the time bar, click Play to start playing the trial data. The data plays through to the end and restarts at the beginning if you do not click Stop.
- Range of frames: Do one of the following:
  - To manually adjust the range, move the blue triangles that indicate the start and end of the selected range of frames (also known as the region of interest) along the timeline; or
  - On the time bar, right-click and then click Set Region-of-Interest. In the Set Region of Interest dialog box, specify the Start Frame and End Frame.
- Individual frame: Move the blue vertical line that indicates the currently selected time along the timeline to manually locate the desired frame, or right-click on the time bar, click Set Current Frame and enter the number of the required frame.

Tip
To display a context menu in which you can reset the timescale on the timeline, set the playback speed, or specify the length of trajectory tails, click the ellipsis (...) in the time bar controls, or right-click the time bar.

Assess trial health with the data Quality pane

The data Quality pane, a tab in the Communications window, provides both a broad overview of data quality for a subject across the entire trial and a way to examine the health of individual trajectories. It also enables you to navigate to the highlighted issues.

The three most common data issues that you need to find and resolve are:

Missing markers (usually knocked off before capture)
Unlabeled or incompletely labeled trajectories
Gaps in trajectories

The Quality tab helps you to find this information:

	Overview of the health of the whole trial (Labeling column) The text in each rectangle indicates the number of unused markers, any gaps, and the percentage of markers labeled. As a quick indicator, to enable you to assess whether to continue working with the trial, the color green indicates good health, red indicates probable major issues, and colors between the two (yellow, amber, orange) indicates that the overall health of the trial lies somewhere between these extremes.
		For example, a good trial, worth further work, would be indicated by: No missing markers A high percentage of labeled markers Only a small number of gaps.
		A low quality trial, which would probably have to be re-run, would be indicated by: Missing markers, and/or A high number of gaps, and/or A lower percentage of labeled markers. In this example, two required markers are completely absent from the trial, so, without further work, you would know that you would have to either re-reconstruct or (more likely) re-capture the trial.
	Individual trajectories. If you hover the mouse over a blob, the blob displays information about the trajectory. If you click on it to select it, information about the trajectory is displayed in the Selection column on the right. For more information, see Navigate to gaps using the data quality features.
	General trial information/selected trajectory Information (Selection column). If no blob is selected, general information about the currently loaded trial is displayed. If a blob is selected, information about the trajectory is displayed.
	Display options (Options column): Enables you to configure the display options for the data Quality tab. Alternatively, you can open the Options dialog box (F7), click Data Quality Panel Options on the left, and change the properties as required. To save any changes to these settings, click the Save current configuration button in the Options dialog box.

Detect gaps in the Graph view

The Graph view enables you to view and fix gaps for a selected trajectory.

To display gaps:

On the Quality pane, click a trajectory blob that is reporting a gap.

Gap indicators are displayed in pink in the Graph view.
To zoom in and out, CTRL+double-click on a gap indicator (the pink area) on the graph.

View gaps with the Data Correction view

The default Data Correction view type displays a 3D Perspective view above a Graph view.

You can turn Data Correction view on or off in the Options dialog box, as described below.

When the Data Correction view is turned on, it is automatically displayed when you navigate using the data Quality pane.

If you would prefer the Data Correction view to appear differently (for example, displaying the Graph above the 3D Perspective view), you can save your own preferred view and select this instead.

To configure the Data Correction view:

Open the Options dialog box (F7).
Click on Data Correction View Options on the left and change the properties as required on the right:
1. If you want to display this view type automatically when you are navigating via the Quality tab, ensure View Type is set to On.
2. If you have saved a different view type to be displayed when you are using the Quality tab, ensure it is selected in the User Specified Data Correction View field.

View data quality across a trial

In addition to viewing data quality on the Quality tab and Graph and Data Correction views, you can also view data quality as a heat map on the time bar, to get an overall picture of the current trial.

To turn on the heat map overlay:

In the Options dialog box (F7), click on Time Bar on the left, and select the Heat Map Visible check box on the right.
If required, change the colors of the heat map.

When you click on a trajectory on the Quality tab, the time bar shows gaps for the selected trajectory.

Viewing data quality for multiple trajectories

To select multiple trajectories, on the Quality tab, CTRL+click the required blobs.

When multiple trajectories are selected, the heat map's color gradient system is activated.

Lighter colors show where one of the trajectories has a gap but other selected trajectories do not. Darker areas show where a number of selected trajectories has a gap.

Two trajectories selected

The following images show two trajectories selected. The darker area indicates gaps in both trajectories.

More trajectories selected

As more trajectories are added the view starts to morph from individuals gaps for one or two trajectories, to areas in the volume/time where there are issues.

Navigate to gaps using the data quality features

Using the Quality tab and the Data Correction view type, you can quickly navigate to gaps in data, and use the Zoom, Translate, and Rotate options for a better view.

Quick navigation to gaps

To quickly navigate to gaps:

On the Quality tab, click on a trajectory blob.Immediately, the time bar and view pane displays the first gap (if any) for the selected trajectory.
To move to the next gap or previous gap for the selected trajectory, press the hot keys CTRL+8 and CTRL+7 respectively.
Tip: On the data Quality tab, you can move to the next trajectory and previous trajectory by pressing CTRL+PgUp and CTRL+PgDown.

Get a better view of gaps

The Zoom, Translate and Rotate options for viewing a gap make it easier to zoom in on and fix selected gaps.

To view gaps more clearly:

In the Options dialog box (F7), click General View Options on the left.
In the Properties pane on the right, in the 3D View Options section, click the Focus on Selection Mode list.
To display a zoomed view that rotates the workspace to a flat perspective of the gap, click Zoom, Translate and Rotate.
On the Quality tab, click the blob for the trajectory whose gaps you want to examine.
The 3D Perspective view zooms in and rotates as necessary to clearly show the selected trajectory's first gap.

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