User guide

Charnwood Dynamics Ltd. Coda cx1 User Guide – Coda Basics I - 1
CX1 USER GUIDE - COMPLETE.doc 26/04/04 32/162
Aligning the Coda cx1 Scanner Units
The Codamotion Analysis program applies an offset and rotational transformation to the
co-ordinates measured by each Coda, so as to reference them to a common room co-
ordinate frame.
When a single Coda unit is in use, the rotational transformation is optional, but the origin
offset must be set for each measurement session (each time Codamotion Analysis is
started). The origin location is not stored. The program will normally not allow data
acquisition until the origin has been set (using the CODA: Define Marker Origin
command).
†
When two or more Codas are used together, both the origin offset and rotational transform
must be applied to ensure that the co-ordinates measured by each unit are referenced to
a common co-ordinate frame.
Origin Offset
The origin offset may be reset at any time, and is independent of any rotational
transformation.
The origin point must be within the field of view of all active Codas, and it must be
possible to place a marker at this point which can be seen clearly by all active Codas
simultaneously. The marker must not be too oblique to any Coda, and there should not
be any reflecting surfaces close by. The origin point should be approximately equidistant
from all active Codas. When a force platform is in use, the origin must be set at its centre.
Any marker may be used to define the origin: select the Define Marker Origin…
command from the CODA menu and enter the marker number. When OK is pressed, the
marker position is measured a number of times to average any co-ordinate noise. If the
marker does not provide a strong enough signal, the operation will fail.
Aligning a Single Coda
A single Coda may be aligned to a room (walkway) co-ordinate frame either physically or
by creating an alignment transformation (rotation) matrix.
If an alignment transform matrix is created, it is stored in a text file
C:\Codamotion\Coda\CXxxxx-Alignment.dat (where xxxx is the Coda unit serial number)
and can be used in subsequent measurement sessions if the Coda has not been moved.
Physical Alignment
The Coda’s co-ordinate frame is accurately aligned with its front plate: the x-axis is the
sideways (long) axis, positive to Coda’s right, the y-axis points forwards, and the z-axis
upward.
The Coda unit may be adjusted physically to the room (walkway) co-ordinate frame using
a spirit level, tape measure etc. Alternatively, place three markers in a triangular pattern
†
It is possible to configure Codamotion Analysis to allow data acquisition without having set an origin by
editing the application’s initialization profile (its INI file in the WINDOWS directory): set the ‘NoConfirmInit’
value in the [AppOptions] section to ‘1’. If an origin has not been set, acquired co-ordinates will be relative to
a point behind Coda’s ‘A’ camera.