How is longitude defined?

Longitude is defined as the angular measurement that specifies the east-west position of a point on the Earth's surface. It is measured in degrees from the Prime Meridian, which is designated as 0 degrees. The measurement extends to 180 degrees east and 180 degrees west, allowing for a comprehensive grid that helps in pinpointing specific locations on the globe. This system is essential for navigation, cartography, and geographic information systems.

The other options, while related to geographical concepts, do not accurately define longitude as precisely as the chosen answer. For instance, measuring from 0 to 60 degrees does not encompass the full extent of longitude, given that it ranges up to 180 degrees. Similarly, while longitude can have a basis in time zones due to the Earth's rotation, this is more about its application rather than its fundamental definition. Finally, describing longitude as a leg of triangular geographical mapping is misleading, as it implies a more static and limited representation rather than the dynamic angular measurement that longitude actually represents.