How to calculate distance between two points when the longitudes and latitudes are known?
That is not an easy answer. The calculation of distance between two pairs of Lat/Long has many variables and is rather complicated. The science that is most appropriate to answer this question is geodesy. The variables required for this calculation include coordinate reference system, datum, spheroid, etc. Most calculators on the internet assume a simple sphere because the mathematics are simpler. To answer your question about some of the formulae used, check this link: http://williams.best.vwh.net/avform.htm It includes several formulas for the great circle calculation. This is aviation related. For more scientific information here is a good start: http://www.ngs.noaa.
