Linear coordinates are coordinates of frame's origin, which is connected with object, relative null frame.

Suppose we have two frames: null frame (NF) and the hard connected with the object frame (OF). Let as turn axes of NF in positive direction in following order: Y (angle P - Pitch), X (angle Y-Yaw), Z (R-Roll). We must turn until each axis of NF coincides with the same axis OF. Angles P, Y, R are said to be angular coordinates of object.