We are in the process of implementing a new Signal in the C3D format that will contain data from PRESSURE platforms and PRESSURE mats.

This is a work in progress, but we feel compelled to share our thoughts. This is an initial draft and all comments are welcome.

When we have settled on a format, we will make a proposal to www.c3d.org.

The signal data will be stored in a new Data block (e.g. not interleaved with the POINT and ANALOG signals) and will have a new set of PARAMETERS.

Contingency for adding new Data blocks has always been part of the c3d format, but it is rarely implemented.

We expect no issues with backwards compatibility because any existing C3D reader will read the parameter section, and safely ignore the data block.

Our prototype implementation is based on the Novel EMED pressure platform].

Physical Parameters implemented:

• sensor area (mm)
• number of sensors
• resolution (sensors/ cm²)
• frequency (Hz)
• dimension (mm) {As with the Force Platform parameters, the dimension is part of the specification of the CORNERS}

Signal1 is stored as a packed array of data The signal has 7 elements element 0= frame number (maybe not needed), element 1= pressure plate number, element 3= sensor number, element 4= X force, element 5= Y force, element 6= Z force, possible future implementation could have COP, etc).

For example 1 - 5, 1, 60, 0, 0, 203 – This is data for frame 5, plate 1, sensor 60, data is 203N Z. 2 - 5, 1, 77, 0, 0, 33 – This is data for frame 5, plate 1, sensor 77, data is 33N 3 - 5, 1, 1037, 0, 0, 44 – Frame 5, plate 1, sensor 1037, data 44N 4 - 5, 1, 2055, 0, 0, 65.3 5 - 5, 1, 3634, 0, 0, 99.4 6 - 5, 1, 3798, 0, 0, 34.5 7 - 5, 1, 3987, 0, 0, 44 8 - 5, 1, 4398, 0, 0, 49 9 - 5, 1, 5634, 0, 0, 45.6 10- 5, 1, 5911, 0, 0, 65.2 – End data for frame 5 11 - 6, 1, 60, 0, 0, 110.6 – Start data for frame 6 … 25 - 6, 1, 4399, 0, 0, 103.8 - Last piece of data for frame 6 26 - 7, 1, 42, 0, 0, 5 – Start data for frame 7 27 - …

Signal2 contains an index Stored for each “pressure” frame an index into the packed data array for that frame. 1 - 0 - No pressure data for frame 1 2 - 0 - No pressure data for frame 2 3 - 0 … 4 - 0 … 5 - 1, 10 – Frame 1 of the packed array has data for frame 5 which contains 10 sensors with a reading 6 - 11, 15 – Frame 11 of the packed array has data for frame 6, which contains 15 sensors with a reading 7 - 26, 3 – Frame 26 of the packed array has data for frame 7, which contains 3 sensors with a reading 8 - 0 - No pressure data for frame 8 9 - 0

C3D Parameters

USED Unsigned Short Number of Pressure Arrays DATA_START The Block number at which the Pressure Data Section starts TYPE RATE The sampling rate of the PRESSURE data RATIO SCALE The scaling factor for the PRESSURE data UNITS The Units in which the POINT data signals are stored in the file. The default value is mm (millimeters). Note that all other PARAMETERS must be consistent with this unit. For example, if the POINT UNITS are mm, the force platform siganls should be scaled to Newtons and Newton-millimeters CELL_SIZE The size of the pressure cell CELL_NUMBER The number of pressure cells INDEX_COMPONENTS The number of components in the Index signal PACKED_COMPONENTS The number of components in the Packed signal INDEX_FRAMES The number of frames of INDEX data PACKED_FRAMES The number of frames of PACKED data LABELS The Label Names of the PRESSURE data signals DESCRIPTIONS The Descriptions of the PRESSURE data signals.