How do I find the distance between two longitude/latitude points?

Question

How do I find the distance between two longitude/latitude points?
I need to know how to find the distance between the two points
(60N, 110W) and (20S, 110W)? Can someone please help me

I need to know the actual method (i.e the formula or conversion to use) not just the answer... :) thanks

Answer 1

Hello,

We will use the earth's radius to be 3963.167 Miles

So the circumference is 2*3963.167*PI = 24888.69

Now Finding the arc length of 1 degree x /1 = 24888.69 /360

x = 69.14 miles.

Now we have 60 - (-20) = 80 degrees giving us 80*69.14 = 5530.82 miles.

Hope This Helps!

So

Answer 2

the formula is
S = r * θ

S = your desired arclength
r = radius of the earth
θ = angle between the two points (it is important that this angle is in radians , not degrees)

the conversion:
angle in degress * (π/180°) = angle in radians.

Now, our formula will be simplistic.. meaning like in your example... we will determine the distance with either the same longitude or the same latitude.

In your example...
angle = (60°+20°) = 80°
......... 80° * (π/180°) = 4π/9 = 1.396263 (in radians)

arclength:
S = r * 1.396263

now.. use an approximation for r. Since the earth is not exactly spherical in shape. It is slightly flatter at the pole...

we can use 3963 mi or 6378 km (or something smaller...) for r.

S = 3963 * 1.396263 = 5,533 miles
S = 6378 * 1.396263 = 8905 km
(the distance might actually be slightly lower than that...)


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