Global and Local Coordinate Systems

Global Coordinate System

• Denoted $X,Y$
• Often attached to Earth but can be attached to other objects as needed
• Absolute positions, velocities and accelerations are with respect to the GCS

Inertial Frame

• System that the coordinate system is attached to has no acceleration itself
• Sign convention:
  • All angles are measured according to right hand rules
  • Counter-clockwise(CCW) angles, angular velocities and angular accelerations are positive in sign.

Local Coordinate System

• Denoted $x,y$
• Attached to a point of interest
• Can be rotating
  • local rotating coordinate system → LRCS
  • local non-rotating coordinate system → LNCS
• Common points of interest: pin joint, center of gravity, etc.
• Use local coordinate systems to make analyses more straightforward
• Necessary when analyzing kinematics