How much ground does ISS cover?

Map from heavens-above.comTwisst-follower @rolandtaams just asked a question I didn't really know the answer to: if ISS travels from West to East over my head, how far does it actually travel?

From looking at the maps in GoSatWatch, I know that when ISS comes up here in the Netherlands, ISS is still above the Atlantic ocean. When it passes high and can be seen all the way to the horizon in the East, it's already above Russia. So that would be about 3.200 kilometers or 2,000 miles.

Let's assume it is visible all the while it passes you, and it travels at 400 kilometers at 7,7 kilometers a second. It would be relatively easy to calculate the distance in space, but how much is that on the ground?

Personally I'm terrible at math, but if you have a suggestion for a method, please tell everyone in the comments below!



wow what a fun site with awesome interactive tool, can't wait for my 1st tweet saying when ISS above me


Nice, can't wait until it flies over my house, thanks!


If one were to track the ISS from horizon (approaching) to horizon (departing), then during this time, the ISS will travel roughly 4275 km.

Disclaimer: I may be slightly wrong, I may be very wrong.


the info Twisst provides is more than clear enough to see the ISS. They provide you with the exact time and the direction it is coming from. All you need to do is look up.

The following site will also help you. In particular check the graphic which shows the flight path, then you can limit your view of the sky to the area it is going to appear.

For me (in Ireland) recently it has been coming up in the SW and leaving in the E/SE so I just look at that area of the sky.


I've never seen an ISS pass either. How much time do I have to spot ISS? minutes? seconds?


Updated. Two versions of how much ground the ISS covers every passing.
This is not considering the curve the ISS is making (the wave pattern with which it is circling the Earth) because it has very few influence, it would differ about 1 kilometer, 0.6 miles, I think.
PDF Kilometers:
PDF Miles:

There might be some small errors in the Miles-version, since I didn't recalculate the actual values, but just used a converter. I do not think it has any significant effect on the actual outcome of the calculations.
If I have time, I might upload an updated version with all the details actually calculated. But right now I'm working on my laptop and running MatLab on my laptop is like trying to move a stubborn donkey. It'll take forever ;)


Imagine a line from the center of the Earth that passes through the point on the ground under the satellite, and then through the satellite. The ratio of distances should allow you to do the calculation. This is what Bruce did in his comment. The radius of the Earth is in thousands of miles while the satellite is but a few hundred miles above us. So, as he says, the speeds don't differ by much.


Full explanation of the distance ISS is covering while theoretically visible in the sky, at what distance it is first visible etcetera.


The distance on the ground and in space will be virtually identical. They will be in the ratio of approximately (6371km + 340km)/6371km = 1.05, so only about 5% different. (the ground track is shorter, of course)


This is the formula I use in Gpredict satellite tracking code:

footprint = 12756.33 * acos (Re / (Re+alt))

Re = Earth radius in km
alt = satellite altitude


You provide us with all this information AND NOW you claim that you're bad at math? No wonder I've never seen an ISS pass.

The fact that I'm really not good in the morning has nothing to do with anything.

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