FIELD GUIDE · Satellites & Orbit
Why the ISS Orbit Looks Like a Wave on the Map
The ISS flies a straight circle — so why is its path on the map a wave?
Open the live ISS map and watch the station for a few minutes. It slides across the world from west to east, and the thin line trailing it and running ahead of it isn't straight — it arcs up toward Europe, dives down across the Southern Ocean, and climbs back up, over and over, like a long rolling wave. Yet the ISS isn't weaving. It's flying the straightest path physics allows: a circle around the middle of the Earth. So where does the wave come from?
A straight circle, drawn on a flattened Earth
The station orbits in a single flat plane that slices through the centre of the planet, tilted 51.6 degrees to the equator. On a globe, the path it traces on the ground below — its ground track — is just a ring wrapped around a sphere. There's no wave anywhere.
The wave appears only when we peel that round Earth open and lay it flat on a rectangular map. A tilted ring, unrolled, becomes an S-shaped curve: it rises to 51.6 degrees north at the top of each loop, slants down across the equator, bottoms out at 51.6 degrees south, and rises again. Every world map you've ever seen does this same violence to straight lines — it's why the shortest flight from New York to Tokyo looks like a big curve arching over the Arctic. The ISS wave is the same illusion. Switch to the globe view and it snaps back into a plain ring.
Why it stops at 51.6 degrees
That 51.6 degree tilt is also a hard latitude ceiling. Because the orbit never leans steeper than 51.6 degrees, the ground track can never climb higher than about 51.6 degrees north or dip lower than about 51.6 degrees south. Draw those two lines on a map — roughly through London and Calgary up top, through the bottom of South America below — and the station lives entirely between them. It has never once flown over the North or South Pole, and it never will on this orbit.
Why that specific angle? It's a compromise of geography, not science. A launch site can most easily reach an orbit inclined at least as much as its own latitude. Baikonur Cosmodrome in Kazakhstan sits near 46 degrees north and, for safety, its rockets fly a track that puts the station at 51.6 degrees — an angle reachable from both Kazakhstan and Florida. Coverage of the poles was simply never the goal.
Why every lap drifts west
Watch long enough and you'll notice each pass doesn't retrace the last — it lands to the west of it. That's not the orbit moving; it's the Earth turning underneath it.
One orbit takes about 93 minutes. In those 93 minutes the planet keeps rotating eastward, sweeping about 22 to 23 degrees of longitude past underneath the orbit. So when the ISS comes back around to the same latitude, the ground below has rotated on, and its track falls about 22 to 23 degrees further west than the loop before. Repeat that sixteen-ish times a day and the whole wavy pattern slowly marches all the way around the globe — which is why, over a day or two, the station eventually passes over almost everywhere between those 51.6 degree lines, including possibly your city.
From "where is it now" to "when can I see it"
The map answers where is it right now. The other question — when will it fly over my town, and which way do I look — is a stargazing question, because the ISS is one of the brightest points in the night sky when sunlight still catches it against a dark sky. That's computed for your exact location on the Sky ISS pages, and the broader art of spotting it is covered in how to see the ISS.
For now, open the live map, find the bright dot, and follow the wave.
Frequently asked questions
Why does the ISS path look like a wave on the map?
The station actually flies a straight great circle around the globe, tilted 51.6 degrees to the equator. The wave is what that tilted circle looks like once you unroll the round Earth onto a flat rectangular map: the track climbs to 51.6 degrees north, crosses the equator heading down to 51.6 degrees south, and climbs back — a rolling S-shape. On a 3D globe there is no wave at all, just a ring; the wave is a side effect of flattening the map.
Why does the ISS never fly over the North or South Pole?
Its orbit is inclined 51.6 degrees, which sets a hard ceiling on how far north or south the ground track can reach — about 51.6 degrees of latitude, roughly the line through London, Calgary or the southern tip of South America. Above that, the station simply never passes. That 51.6 degree angle was chosen so rockets from both the US and Baikonur in Kazakhstan can reach it, not for coverage — so the far polar regions are permanently off its route.
Why does each orbit appear shifted to the west?
One lap takes about 93 minutes, and in those 93 minutes the Earth keeps spinning underneath — turning roughly 22 to 23 degrees of longitude to the east. So by the time the ISS completes a loop and crosses the same latitude again, the ground below has rotated on, and the new track lands about 22 to 23 degrees further west. Sixteen laps later the pattern has walked all the way around the planet.
How fast is the ISS moving, and how long is one orbit?
The ISS travels at roughly 7.66 kilometres per second — about 28,000 km/h, or 17,100 mph — orbiting around 400 to 420 km up. At that speed one full orbit of Earth takes about 93 minutes, so the crew see roughly 16 sunrises and 16 sunsets every day.
Is the moving dot the real position of the station?
Yes. The dot is computed live from the station's published orbital elements using the standard SGP4 model, the same maths used to predict satellite passes. It is a genuine calculated position updated continuously, not a recording — accurate to well within the width of a city.
SEE IT LIVE
Everything in this guide is on one real-time map.