and yes, it's FS related.I'm trying to set a spreadsheet up so that it will calculate straight-line distances between two points. And since I never did do well in math I need a little help.Assume two points, x,y and a,b where:X=decimal based longitude of the first pointY=decimal based latitude of teh second pointa=decimal based longitude of the second pointb=decimal based latitude of the second point.Now, what formula do I use in the spreadsheet cell to make it calculate a straight line distance, in nautical miles that takes into effect the fact that the earth isn't as big around at higher latitudes than it is at the equator.How do I do this???BobL

Hi,You need the great circle calcs, wrestle through:http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchHope it helps,Jan"Procul Negotiis"

Hi,I think you should check the webpage of this math genius. I have used it several times:http://williams.best.vwh.net/avform.htmEgbert