Parameter interpretation

The C3D environment is very flexible because all data collection environments are different, the C3D parameters exist to try and allow users to identify and process the data, regardless of the environment that created it.  The parameter concept can result in collections of parameters that document the contents of each analog channel and the interpretation but it’s common to see C3D files that only contain data with identical LABEL and DESCRIPTION parameters without any data specific information as a result of applications written to create and process C3D data by programmers without any clinical or biomechanics lab experience.

The C3D format evolved in the NIH biomechanics lab under the direction of a professor of Kinesiology and Applied Physiology working with in the biomechanics, human anatomy, and exercise physiology fields to collect and process biomechanics gait movement information for NIH clinicians and researchers working with many labs.  As a result the C3D format was designed with parameters to document and describe the data, so each analog channel of data is described by a set of parameters, ANALOG:LABEL, ANALOG:DESCRIPTION, ANALOG:SCALE, ANALOG:OFFSET, and ANALOG:UNITS.

The parameter concept is that each analog channel has a unique machine readable LABEL and a human readable DESCRIPTION – the LABEL allows software to identify each channel and the DESCRIPTION records the channel contents in human (and culture specific words) for the users.  The aim is to allow data to be recorded in different environments, while users can identify the data from the DESCRIPTION, and software applications can process it by referencing the LABEL and determine the associated SCALE, OFFSET, and UNITS parameters to accurately process the data.

If the C3D design is supported then users can open files from many different environments and determine the contents in each file.  This allows the software to process the data based on the associated LABEL reference – for example one file might contain data identified as “Right Ant Tib” and stored as millivolts in analog channel 12 labeled EMG12 while another file might contain “Reit Tib Ant” in analog channel 43 store as volts and labeled REMTA – the users software can then process both data sets by referencing the LABEL parameters that the user identifies as indicating the analogue channels containing the relevant data by looking at the human readable DESCRIPTION parameters.

The LABEL is intended to be machine readable (e.g. EMG01 stored as 7-bit ASCII characters) while the associated DESCRIPTION is human readable (e.g. bicep femoris, bíceps femoral, or dikéfalos miriaíos, stored as UTF-8 characters)  – so all data processing environments can reference the LABEL reliably while displaying the DESCRIPTION to support the users local language.  This can result in a C3D file that is universally accessible in virtually all environments, allowing data to be collected, shared, and processed, worldwide.