What is the definition of dead-reckoning?
In the 1600s, navigators aboard ships came up with the term “dead-reckoning” to describe the technique of estimating course and distance in situations where there were no visible landmarks or stars available for guidance.
The term used to estimate velocity, direction and distance travelled from a last known position without external aiding such as via GNSS. An INS is typically used for dead-reckoned navigation.
Read more “Dead reckoning for GNSS denied scenarios – an introduction“
The red vehicle is an attempt to follow the trajectory of the blue vehicle using dead-reckoning by an INS (Inertial Navigation System) only. That is, the INS accelerometers and gyroscopes are estimating linear acceleration and rate of rotation, with an internal timing clock reference. As you can see, there are discrepancies between the two trajectories due to limitations in sensor accuracy and a tendency for sensors to drift. Note that inaccuracy and drift is exaggerated for illustrative purposes.
The trajectory for the blue vehicle is:
- Move straight ahead from (A) 7.5 m to (B) in 3 s.
- Rotate 45° counterclockwise, move straight ahead from (B) 22.5 m to (C) in 5 s.
- Rotate 135° clockwise, move straight ahead from (C) 42.5 m to (D) in 9.5 s.
- Rotate 30° clockwise, move straight ahead from (D) 15.8 m to (E) in 5 s.
At the end of the journey, the blue vehicle should have travelled 88.3 m over 22.5 s (not including time required for rotation). The red vehicle is close to the blue vehicle, however, some distance away in terms of position and heading.
