Estimated Position (EP) is based on what?

• A. Based on four LOPs
• B. Based on two LOPs or an LOP and DR position taken at the same time
• C. Based on a single LOP
• D. Based on set and drift only

Answer: (B)

Estimated Position relies on lines of position derived from observations. You need at least two lines of position, or one line of position plus your dead-reckoning (DR) position taken at the same time, to determine a single estimated position. Two LOPs intersect to give the fix; a single LOP only defines a line and can’t pinpoint where you are along it. If you can’t obtain a second LOP, combining one LOP with the DR position provides a single EP estimate. Set and drift describe currents affecting motion and don’t by themselves yield a position fix.