Event
Capture
Correlation
Settings
The Event Capture Settings dialogue has two sections. The Event Capture section defines the event which should be searched for, the trajectories and how many frames of data should be recorded for that event. The Correlation Settings define how the data should be correlated with the new trial data, and which name to use for the generated events.
This specifies the type of event that should be captured. Vicon
Workstation allows the manual definition of events using the time cursor and
the buttons on the Time Bar. There are three different types of event - Foot
Strike, Foot Off, and a General event (which is normally given the text label
"Event"). Select the event type as appropriate, depending on how you define
the event manually.
Select the context this event should be found in.
When an event is captured in a particular context, when the correlation stage takes place and events are generated, they will be generated in the same context.
The list box shows the trajectories that should be sampled at the time the
event occurs. Use the Add, Edit and Delete buttons to change the trajectory
labels. The Add and Edit buttons will bring up the Trajectory Label dialogue.
Use the Before and After boxes to define the number of frames either side
of the event that should be captured. Points for each of the trajectories in
the trajectory list will be saved in the captured events data file, and used
later for correlation. See the notes in Event Correlator
Help for more help in deciding which settings to use, and Succesful Event
Detection for some general hints.
You can choose which component of the points in the trajectory should be
considered for the calculation of the correlation coefficient. Choosing the
right component can be important in achieving a good sensitivity in the
correlation process, without making the correlation too specific to the
captured event.
Use this setting when all three of the
components are important, and you know that the marker is always going to be
moving in basically the same direction in the laboratory space (e.g. when
practicing golf swings) or when the trajectory holds other data (e.g. joint
angles) which consistently have the same basic curve shape.
Use this option when you are correlating a
marker (or other point) whose horizontal direction may change from one trial
to the next (e.g. in different gait trials where the subject walks in either
direction). Since the X and Y values are combined in the correlation, it can
be less sensitive than the Independent XYZ option.
Use one of these options to limit the
correlation to the given component. For example you might use this to detect
an event when the hip abduction angle changes in a particular way.
This option combines the three components of
each point before performing the correlation. This allows a correlation to be
made for markers regardless of their direction (e.g. you could correlate an
unusual but characteristic hand motion, which occurs at unpredictably times
during walking). However, this is the least sensitive of the options.
This option allows you to change the name of the captured event to
something more appropriate, rather than using the names given by the preset
definitions in Workstation. Naming your events becomes particularly important
when are using the ParameterCalculator PlugIn to take measurements from your
trial.