Pikkusgraadi

Pikkusgraadi, often shortened to graadi, is a unit of angular measurement used to express the longitudinal position of a point on Earth's surface relative to the Prime Meridian. It is one of the two coordinates, alongside latitude, that define a location on the globe. Pikkusgraadi measures the angle, in degrees, minutes, and seconds, east or west of the Prime Meridian, which passes through Greenwich, London.

A full circle is divided into 360 degrees. Therefore, pikkusgraadi values range from 0° at the Prime Meridian to 180° east and 180° west. Locations to the east of the Prime Meridian are designated as East pikkusgraadi (E), while those to the west are West pikkusgraadi (W). The International Date Line generally follows the 180° meridian.

The concept of pikkusgraadi was crucial for navigation and cartography throughout history, enabling sailors and explorers to determine their precise position at sea. Accurate measurement of pikkusgraadi became significantly more feasible with the development of reliable chronometers, which allowed for the determination of local time relative to Greenwich Mean Time. Understanding pikkusgraadi is fundamental to global positioning systems (GPS) and geographical information systems (GIS).