Enumerated names for the Dead Reckoning Model (DRM) are formed by a combination of letter codes. Following is a description of the letter codes: F - Fixed orientation; angular velocity not used R - Rotating; orientation extrapolated using angular velocity P - Position extrapolated using linear velocity; acceleration not used V - Velocity and position extrapolated using velocity and acceleration W - Linear velocity and acceleration provided in world coordinates B - Linear velocity and acceleration provided in body coordinates; angular velocity required for all extrapolation