The zero line of longitude from Greenwich, with all 8 countries it passes through.
How this tool works
The Prime Meridian is the reference line of 0 degrees longitude adopted internationally in 1884, running through the Royal Observatory at Greenwich in London. The map draws the line at its exact astronomical position on an equal-area style world map, and the table below it lists every country the line crosses. Entry points and approximate overland lengths are computed by intersecting the line with country boundary polygons, so the figures are estimates based on simplified boundaries rather than survey values. Note that modern GPS uses the IERS reference meridian, which lies about 102 meters east of the historic Greenwich line.
What you can do with it
- See the 8 countries on the line: the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Ghana, and Togo
- Compare overland lengths per country
- Use it to explain longitude, time zones, and why Greenwich was chosen
- Check the small offset between the historic line and modern GPS zero
Why use it
Most maps show these lines as unlabeled dashes with no detail. If you want to know exactly which countries a line passes through, and for roughly how far, you usually end up cross-referencing several articles. This page puts the line, the country list, and the lengths in one place.