Which reference point is considered the starting point for measuring longitude?

The Prime Meridian is the starting point for measuring longitude because it is defined as the meridian at 0 degrees longitude. Established at the Royal Observatory in Greenwich, London, the Prime Meridian serves as the reference line from which all other longitudes are calculated, extending 180 degrees east and west. This convention allows for a standardized system that facilitates navigation and mapping across the globe.

While the Equator is critical for measuring latitude, it does not play a role in determining longitude. Greenwich, although it refers to the location where the Prime Meridian is established, does not define the measurement itself; it is the Prime Meridian that acts as the reference point. The North Pole, while significant for geographic orientation, is not used for measuring longitude, as it does not represent a specific meridian or line of longitude.