If the POINT:SCALE parameter is positive then the 3D data section will contain signed integer format data for each stored trajectory.  Note that the POINT:SCALE parameter is one of the parameter section values that is copied to the C3D file header (words 7-8) as can be quickly located and read by software applications without requiring a detailed search of the parameter section.  The 3D integer point record is organized as follows:

 

Word	Contents (signed integer format)
1	X co-ordinate of point divided by the POINT:SCALE factor.
2	Y co-ordinate of point divided by the POINT:SCALE factor.
3	Z co-ordinate of point divided by the POINT:SCALE factor.
4	Byte 1: cameras that measures marker (1 bit per camera) Byte 2: average residual divided by the POINT:SCALE factor.

Figure 19 – 3D point data storage using INTEGER format.

The first three signed integer words record the X, Y, and Z co-ordinate values of the 3D data point, divided by the floating point POINT:SCALE parameter value.

Word four of the 3D point record is comprised of two bytes.  The first byte records which observers (normally cameras) provided information used in calculating the 3D point, while the second byte contains the average residual for the 3D point measurement.  The 3D point residual is a measurement that provides information about the relative accuracy of the 3D measurement and must be multiplied by the POINT:SCALE parameter to obtain the scaled value.

Figure 20 - Residual and mask storage - Integer format.

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Notes for Programmers - Integer 3D Data