Motion specific data (motion\)

Within each motion specific folder, the data files are organized as follows:

.
├── sourcedata/
├── rawdata/
    ├── sub-<label>
        ├── motion/
            ├── sub-<label>_task-<label>_tracksys-<label>_channels.tsv
            ├── sub-<label>_task-<label>_tracksys-<label>_motion.tsv
            └── ...
        ├── ...
        └── sub-<label>_scans.tsv

The data are stored in text-based format, and are TAB delimited. In this way, data can be read into MATLAB, Python, or even Excel. However, if the files become too large, the user can change the file format e.g. .npy, but keeping the same tabular structure. The full template would read as follows ([] means optional):
sub-<label>[_ses-<label>][_task-<label>][_run-<index>][_tracksys-<label>]_motion.*

Channels description (*_channels.tsv)

└─ sub-<label>\
    └─ \[ses-<label>]\
        └─ motion\
            └─ sub-<label>[_ses-<label>][_task-<label>][_tracksys-<label>]_channels.tsv

This file is REQUIRED as it makes it easy to browse or query over larger collections of datasets. The REQUIRED columns are channel name, type, tracked_point, tracking_system, component and unit. Any number of additional columns may be added to provide additional information about the channels.

The columns of the channels description table stored in *_channels.tsv are:

MUST be present:

Key name	Requirement level	Data type	Description
name	REQUIRED	string	Label of the channel. Entries have to match headers in (any) *_motion.tsv.
tracked_point	REQUIRED	string	Label of the point that is being tracked, for example, label of a tracker or a marker (“LeftFoot”, “RightWrist”).
type	REQUIRED	string	Type of data.
component	REQUIRED	string	Component of the representational system described in *_coordinatesystem.tsv that the channel contains.
units	REQUIRED	string	Physical unit of the value represented in this channel, for example, vm for virtual meters, radian or degrees for angular quantities. See the BIDS spec for guidelines for Units and Prefixes.
sampling_frequency	REQUIRED	number	Nominal sampling rate of the channel in Hz.

SHOULD be present:

Key name	Requirement level	Data type	Description
placement	RECOMMENDED	string	Placement of the tracked point on the body (for example, participant, avatar centroid, torso, left arm). It can refer to an external vocabulary for describing body parts.
description	OPTIONAL	string	Brief free-text description of the channel, or other information of interest.

Restricted keyword list for column type in alphabetic order (shared with the other BIDS modalities?). Note that upper-case is REQUIRED:

Keyword	Description
ACC	Acceleration
ANGACC	Angular acceleration
ANGVEL	Angular velocity
ORNT	Orientation
POS	Position in space
VEL	Velocity
TIMESTAMPS	Timestamps of recorded samples

Restricted keyword list for column component in alphabetic order (shared with the other BIDS modalities?). Note that upper-case is REQUIRED:

Keyword	Description
x	entity along the X-axis
y	entity along the Y-axis
z	entity along the Z-axis

Example channels.tsv:

name		  tracked_point		type	    component	     units      sampling_frequency
t1_acc_x	  LeftFoot	        ACC	        x		         m/s^2      200
t1_acc_y	  LeftFoot	        ACC	        y		         m/s^2      200      
t1_acc_z	  LeftFoot	        ACC	        z		         m/s^2      200
t1_gyro_x	  LeftFoot	        ANGVEL	    x		         rad/s      200
t1_gyro_y	  LeftFoot	        ANGVEL	    y		         rad/s      200
t1_gyro_z	  LeftFoot	        ANGVEL	    z		         rad/s      200