The meridian is
|“||an imaginary great circle on the Earth's surface passing through the North and South geographic poles. All points on the same meridian have the same longitude.||”|
|“||[a] great circle on the earth that passes through the poles, often used synonymously with longitude. Meridians run north–south between the poles. By convention, meridians are labeled with positive numbers that ascend as one moves eastward from the prime meridian, and negative numbers as one moves westward from the prime meridian until the east and west hemispheres meet at the 180-degree line. Meridians can also, however, be labeled with all positive or negative numbers, including positive numbers increasing westward from the prime meridian.||”|
- ↑ Georeferencing: The Geographic Associations of Information, Glossary, at 231.
- ↑ Wiki.GIS.com, GIS Glossary (full-text).