Where is the Central Meridian?

What is the central meridian?

The central meridian is the centerline of longitude for projection systems.
Projected coordinate systems often use it as a reference point for an x-origin.
For example, the state plane and UTM projection systems use a central meridian.
Here are some examples of the central meridian in coordinate systems.

3. State Plane Coordinate Systems use a central meridian

Depending on the size and shape of a state, the State Plane Coordinate System (SPCS) uses 1 of 3 projection systems:

• Transverse Mercator
• Lambert Conformal Conic
• Hotine Oblique

For zones that are long in the north-south direction, it uses a Transverse Mercator projection. Just like the UTM system, it has a central meridian and two small circles. If the zone is long from east to west, SPCS uses the Lambert Conformal Conic projection. This projection uses a secant cone and has two standard parallels. When zones are long in the diagonal direction, the Hotine Oblique projection uses a cylinder at an angle with a central line. Transverse Mercator, Lambert Conformal Conic, and Hotine Oblique make up the projections for the SPCS.

4. Where is the central meridian?

The central meridian depends on which projection system you use.
For example, each UTM zone uses the central meridian as an origin for X-coordinates (eastings).
Everything in the central meridian is assigned a value of 500,000 m.
This means that the UTM system has 60 central meridians for all of its UTM zones.

5. UTM Zones

Here is a list of all the UTM zones including the central meridian and the extent of the UTM zone.

Table of contents

• Latitude, Longitude and Coordinate System Grids
• Where is the Central Meridian?
• Greenwich Meridian (Prime Meridian)
• Lost in Null Island: The Curious Origin of 0,0
• Degrees/Minutes/Seconds (DMS) vs Decimal Degrees (DD)
• What is a Horizontal Datum Reference Frame?
• Vertical Datum – Earth's Elevation Reference Frame