Standard meridian
Topic: Latitude, Longitude and Time · NCERT: Class 11, Ch 3 "Latitude, Longitude and Time"
Meaning
The standard meridian is the meridian whose local time becomes the standard time of a country or zone. If every town kept its own sun-based time, one country would have many clock times. A single standard meridian gives everyone one uniform time. By convention it is a multiple of 7°30′, which equals half an hour of time, so the country's offset from Greenwich is a whole or half hour. Countries that are wide from east to west, such as Russia (11 zones) and the USA, use several standard meridians.
Example
India's standard meridian is 82°30′E, which passes near Mirzapur in Uttar Pradesh. 82.5 × 4 minutes = 330 minutes, so IST is 5 hours 30 minutes ahead of Greenwich.
Don't confuse with
- Prime Meridian: this is the 0° line through Greenwich, from which all longitudes are measured. A standard meridian is chosen by each country for its own clock time.