子午線

1. Origins, structure, and basic meaning

• Structure: 子午線 is read しごせん and refers to a meridian joining the Earth's poles.
• Basic usage: It is used in describing positions on globes and maps; longitude is measured from a reference meridian.

2. Common pitfalls and similar expressions

• Longitude and latitude
  • 経度 gives east-west position, while 緯度 gives north-south position. 子午線 is not a line of latitude parallel to the equator.