What is relative navigation used for in navigation systems?

• A. Global positioning in a fixed reference frame.
• B. Estimating only the trajectory of satellites.
• C. Estimating the motion between two states or along a path.
• D. Determining atmospheric delays.

Answer: (C)

Relative navigation is about how an object moves with respect to a reference or another state, focusing on changes in position, velocity, or pose from one instant to another rather than where it sits in an absolute, fixed frame. This makes it ideal for determining the motion between two states or along a path, such as tracking how a vehicle’s state evolves over time or how two vehicles move relative to each other. In contrast, absolute positioning assigns a location in a global reference frame, orbital trajectory estimation deals with the path of satellites, and atmospheric delays relate to correcting signal propagation—topics that aren’t about relative motion between states.