All the Earth mumbojumbo we talked about   Ive done an Excel database to solve the problem of the perimeter of an ellipse and also a Word document explaining how to find the distance between two coordinates on Earth You can download it at  I am sure there are other more sophisticated ways to look for a solution but Ive done it according to my maths level Im used to cartesian coordinates and I know very few things about differential calculus  This solution I found does have an accuracy of millimetres Ground elevation isnt mentioned I believe that is elementary Also I want to acknowledge that after all I dont believe that the Earth is perfectly spheroidal and I think you think that also  There probably is a more accurate Earth equation within some NASA department describing surface irregularities etc I once heard that within its spheroidal shape the Earth has a pearshaped tendency it is thinner at the top and fatter at the bottom Hey but whatever This is what Ive been able to do with the data available and its more than enough P  Please do tell me if the Excel database works fine Ive never checked language compatibility before so I dont know whether it will or it wont Id also be very grateful if you mention any mistake you may see within the formulas in the Word document Thank you for the attention youve given to the matter until now P