What is the Central Meridian?

The central meridian is the inside line of longitude for projection systems.

projected coordinate systems often use it as a kind of perspective point for an x-region.

Here are a few instances of the central meridian in coordinate systems.

Lines of longitude run north-south

Latitude lines run east-west and are corresponding to one another. While lines of longitude run north-south and in the long run combine at the poles.

For instance, the prime meridian is a line of longitude at 0°. Everything along this line has a 0° longitude coordinate.

But, the prime meridian (Greenwich meridian) is explicit to 0° longitude. Much the same as how the equator isolates north and south, the Greenwich meridian isolates east and west.

Projection systems use lines of longitude like the prime meridian. Much the same as how the prime meridian parts east and west, central meridians do the same thing.

UTM system uses a central meridian

If you move 3° toward the east from the prime meridian, this is the focal meridian for UTM zone 31. We dole out all X-facilitates (eastings) on the focal meridian an estimation of 500,000 m.

This central meridian is a discretionary worth advantageous for maintaining a strategic distance from any negative easting coordinates.

Each UTM zone is 6° wide. So for UTM zone 31, it ranges from 0°E to 6°E longitude. At that point, UTM zone 32 is from 6°E to 12°E with a focal meridian of 9°E.

The Transverse Mercator takes a chamber and places it on its side (pivots it 90°). At that point, the chamber converges the ellipsoid along two little circles corresponding to the central Meridian.

State Plane Coordinate Systems use a central meridian

Depending upon the size and state of an express, the State Plane Coordinate System (SPCS) uses 1 of 3 projection systems:

 Transverse Mercator

 Lambert Conformal Conic

 Hotline Oblique

For zones that are long in the north-south heading, it utilizes a Transverse Mercator projection. Much the same as the UTM framework, it has a central meridian and two little circles.

If the zone is long from east to west, SPCS uses the Lambert Conformal Conic projection. This projection utilizes a secant cone and had two standard parallels.

When zones are long in the corner to corner heading, the Hotline Oblique projection uses a cylinder at an angle with a central line.

Where is the central meridian?

The central meridian depends upon which projection system you use.

For instance, each UTM zone utilizes the focal meridian as a starting point 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.

UTM zones (Central meridian)

UTM Zone	Central Meridian	UTM Zone Extent
1	177°W	180°W-174°W
2	171°W	174°W-168°W
3	165°W	168°W-162°W
4	159°W	162°W-156°W
5	153°W	156°W-150°W
6	147°W	150°W-144°W
7	141°W	144°W-138°W
8	135°W	138°W-132°W
9	129°W	132°W-126°W
10	123°W	126°W-120°W
11	117°W	120°W-114°W
12	111°W	114°W-108°W
13	105°W	108°W-102°W
14	99°W	102°W-96°W
15	93°W	96°W-90°W
16	87°W	90°W-84°W
17	81°W	84°W-78°W
18	75°W	78°W-72°W
19	69°W	72°W-66°W
20	63°W	66°W-60°W
21	57°W	60°W-54°W
22	51°W	54°W-48°W
23	45°W	48°W-42°W
24	39°W	42°W-36°W
25	33°W	36°W-30°W
26	27°W	30°W-24°W
27	21°W	24°W-18°W
28	15°W	18°W-12°W
29	9°W	12°W-6°W
30	3°W	6°W-0°
31	3°E	0°-6°E
32	9°E	6°E-12°E
33	15°E	12°E-18°E
34	21°E	18°E-24°E
35	27°E	24°E-30°E
36	33°E	30°E-36°E
37	39°E	36°E-42°E
38	45°E	42°E-48°E
39	51°E	48°E-54°E
40	57°E	54°E-60°E
41	63°E	60°E-66°E
42	69°E	66°E-72°E
43	75°E	72°E-78°E
44	81°E	78°E-84°E
45	87°E	84°E-90°E
46	93°E	90°E-96°E
47	99°E	96°E-102°E
48	105°E	102°E-108°E
49	111°E	108°E-114°E
50	117°E	114°E-120°E
51	123°E	120°E-126°E
52	129°E	126°E-132°E
53	135°E	132°E-138°E
54	141°E	138°E-144°E
55	147°E	144°E-150°E
56	153°E	150°E-156°E
57	159°E	156°E-162°E
58	165°E	162°E-168°E
59	171°E	168°E-174°E
60	177°E	174°E-180°E

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