Meridian Longitude [ Reliable · 2026 ]

This convergence is why polar maps are often displayed using different projections (like the Azimuthal projection) rather than the standard Mercator projection, which grotesquely exaggerates the size of polar regions.

For precise navigation, degrees are broken down:

While thousands of meridians exist, a few stand out for human geography:

Unlike latitude, which has fixed lengths, the distance of one degree of meridian longitude varies dramatically depending on your latitude. meridian longitude

Verdict: Avoid “meridian longitude” in formal writing. Use “longitude” for the coordinate and “meridian” for the line.

Final rating (as a phrase):
🔴 Redundant / Non‑standard – not grammatically wrong, but imprecise and unnecessary. Prefer “longitude” or “line of longitude.”

Example of best practice:
❌ “The meridian longitude of Cairo is 31°14′ E.”
✅ “The longitude of Cairo is 31°14′ E.”
✅ “Cairo lies on the 31°14′ E meridian.” This convergence is why polar maps are often

Meridians and longitude form the geographic coordinate system used to specify positions on Earth east and west of a reference meridian. Longitude is an angular measurement (in degrees) from the prime meridian; meridians are the imaginary north–south lines connecting the poles at constant longitude.

While GPS does this for us now, understanding the manual calculation illuminates the concept. Here is the basic formula:

Longitude = (Greenwich Mean Time – Local Mean Time) × 15° Conversely, if your local noon occurs after GMT,

Step-by-step:

Conversely, if your local noon occurs after GMT, you are West.

Every point on Earth has an address. We know latitude tells us how far north or south we are, but longitude—the unsung hero of navigation—runs north-south, connecting the poles and splitting the planet into time zones. These vertical lines are called meridians, and one of them changed the world forever.

Here’s where it gets practical: Every 15° of longitude equals one hour of time difference. That’s why: