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# Pre-defined types

ProCalc provides many pre-defined types that define specific entities that are meaningful in the context of kinematic or kinetic analysis of 3D motion data. These types are used for all calculations. The following types are defined:

• Number. A floating-point value with or without a unit, for example 15.6kg.
• Angle. A single-component angle with unit in degrees or radians.
• Voltage, Length, Time, Percentage, Frequency. Numbers where the units are fixed.
• Point. A specific location in 3D space, for example the location of a marker or a calculated joint center. Points always have a length-based unit such as mm or m.
• Vector. A direction in 3D space and can be visualized as an arrow. For example, a vector could define the direction from one point to another, the direction of movement, or a velocity.
• Euler Angle. A 3D angle that describes the rotation between two segments, or between a segment and the global reference frame.
• Moment, Force, Power. 3D kinetic variables, either calculated by a biomechanical model or measured by a force plate.
• Line. A line has a location and a direction in 3D space. It is defined by a point that the line passes through, and a vector that defines its direction. A line does not have a start or end point.
• Plane. A plane is defined by a point which is contained in the plane as well as a vector that defines the plane's normal vector.
• Rotation. A rotation is a 3x3 rotation matrix that describes the 3D rotation from one segment to another. A rotation can be decomposed to Euler angles.
• Segment. A segment has both a 3D location and orientation in space. Its location is defined by the position of its origin, whereas the orientation by its rotation from the global (laboratory) coordinate system.