The observed position.

The position obtained by the intersection of two or more position lines obtained from the observation of heavenly bodies is known as the observed position. It is shown on the chart as a dot surrounded by a circle, with “Obs” and the time written next to it.

Observed position formed by the intersection of three astro position lines.

Dead reckoning position (DR).

A position obtained from the course steered by the ship and her speed through the water and nothing else is known as “ a dead reckoning position” and is only an approximate position. The name “dead reckoning” comes from “deduced reckoning” which was abbreviated to “ded reckoning” and later became “dead reckoning”. It is marked on the chart as a small cross with the time alongside it.

Ship’s track with three dead reckoning positions.