Which inputs define Dead Reckoning when estimating position between fixes?

• A. Using a Single Landmark to Determine Position.
• B. Course, Speed, and Time Since Last Fix.
• C. Distance and Bearing to Two Objects.
• D. Ranges to Radio Beacons.

Answer: (B)

Dead Reckoning estimates where you are by moving forward from the last known position using your motion parameters. To do this between fixes, you need three things: the direction you’re steering (course), how fast you’re going (speed), and how much time has passed since the last fix (time). With those, you multiply speed by time to get the distance traveled, then lay that distance off along the course from the last known position to get the current estimate. This is precisely what DR is designed for: continuing to position yourself when you don’t have a new fix from external references.

Other methods rely on external references like landmarks or objects to determine position, or on beacon or range measurements. Those are not Dead Reckoning, which depends only on your last position and your own motion inputs.