Cal Maritime Navigation Test One Practice 2026 - Free Navigation Practice Questions and Study Guide

The main idea is that the Prime Meridian is the zero-degree line of longitude used as the reference for measuring east and west around the globe. It is defined by the meridian that passes through the Royal Observatory in Greenwich, England. This specific line is designated 0° longitude, which is why all other longitudes are measured relative to it. The Greenwich reference provides a universal starting point for navigation, timekeeping, and mapmaking.

So the hallmark is the Greenwich connection: the meridian that runs through the Royal Observatory establishes 0° longitude. The other statements don’t fit because the Prime Meridian isn’t near Paris, isn’t the equator (which is a latitude line, not a longitude), and while a meridian is a line from pole to pole, the defining feature here is its Greenwich location as the 0° reference.