Computation of Distance

We have seen that there is a direct relationship between distance and the longitude or latitude. We can easily compute the aerial distance between the two points on earth if we know their coordinates accurately. For rough computations of distance, we may simply add up the difference of longitude and latitude and equate that to miles. 
Example : Calculate the distance between Delhi and Mumbai approximately.


Distance between two points on the earth's surface having longitude and latitude L1, f1 and L2, f2 respectively can be computed accurately by first computing the angular distance between the following points by the following formula :
Cos d = Sinf1.Sinf2+Cosf1.Cosf2.Cos (L1-L2) 
then computing the required linear distance by the following formula :- S = 6371p d/180 km.
where d is expressed in degrees.
(Note: The formula does not work well for very small values of d)
Example : Calculate the distance between Delhi and Mumbai, taking the following coordinates.

 

Note : - The result is accurate up to a few Km. The inaccuracy is mainly due to flattening of the earth, which has been ignored in the present formula.