All the Earth mumbo jumbo we talked about I ve 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 I ve done it according to my maths level I m 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 isn t mentioned I believe that is elementary Also I want to acknowledge that after all I don t 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 pear shaped tendency it is thinner at the top and fatter at the bottom Hey but whatever This is what I ve been able to do with the data available and it s more than enough P Please do tell me if the Excel database works fine I ve never checked language compatibility before so I don t know whether it will or it won t I d also be very grateful if you mention any mistake you may see within the formulas in the Word document Thank you for the attention you ve given to the matter until now P