Can anyone tell me how to calculate the surface area of a grid cell (1x1 degree) on earth (i.e 180 x 90 degrees for N hemisphere). I need the answers in m^2 assuming I know the longitudes and latitudes.

If anyone has any links too then I would be grateful.

I think I have devised a routine that will work to find this out.


A = (2πr_pol)/360 × &frac12[r_eq(2π/360)(cos lat₁ + cos lat₂)]

Where r_pol and r_eq are the polar and equatorial radii of the earth respectively. What I've called lat₁ and lat₂ are the two lines of latitude between which you need to find the area (they should be only one degree apart).

Perhaps one of the brighter members of the board (everyone except me :) ) could scrutinise this formula to see if it is valid.

You'll probably notice that there are a few simplifications you can make before you compute anything, I just left it like this so it might be easier for people to see how I derived it because I can't be bothered to explain it step-by-step.

Oh, and just make sure to put the radii in metres and the answer will come ot in units of m².

Doing it that way for lats 53N and 54N (and assuming r(pol) = r(eq)) , I got 7.35E+09 m^2

Can anyone else verify this? Would this be a realistic surface area?

That's equivalent to a square 86 km on a side. Does that sound reasonable?

Originally posted by AD1
That's equivalent to a square 86 km on a side. Does that sound reasonable?

Well I measured the area on an atlas using a ruler and scale and I got 7,500 sq km. I think 1 sq km has a million sq ms so the figure is 7.5E+09 which is close enough to validate your method. Thank you!