When I asked this question earlier there was an error in my reasoning. Here is a better way to state it:How do I find the distance between these two lat/long points in feet, where the coordinates are presented in decimal format?Point 1: Lat 42.984665, Long -87.831505Point 2: Lat 42.98461957, Long -87.83139252I

I use this:decimal y = (toPoint.Latitude.Radian - fromPoint.Latitude.Radian) * (40007000.0M / (decimal)(2.0 * Math.PI));decimal x = (toPoint.Longitude.Radian - fromPoint.Longitude.Radian) * (40075000.0M / (decimal)(2.0 * Math.PI)) * (decimal)Math.Cos((double)(toPoint.Latitude.Radian + fromPoint.Latitude.Radian) / 2.0);Don't mind the casting (datatypes in brackets). As you can see, I use radian instead of degrees, so you would have to adjust that.The constants used are from the FS SDK, and as far as I can see, this is very accurate when placed in FS.Output is in meters, so you would need to convert to feet.

Hmmmm, I would have no idea how to actually implement that code. I'm kind of new to all this. Also, I'm doing these calculations in Excel, not FS.

Hi Christine,I made a flight planning program, using Excel, and, as part of this program, I calculate distances between two airports.The formula I use is : =2*3437,74677*ASIN(RACINE(PUISSANCE(SIN(($R$2-G5)/2);2)+(COS($R$2)*COS(G5)*PUISSANCE(SIN(($S$2-H5)/2);2))))The answer is in NM.The latitude and longitude of the 1st point are $R$2 and $S$2.The latitude and longitude of the 2nd point are G5 and H5.The latitudes and longitudes are in radians.If you want to convert deg/min/sec in radians, you have first to express deg/min/sec in decimals : deg(decimal)=deg + min/60 + sec/3600, and multiply deg(decimal) by pi/180.Oh ! yes ! I use Excel in french : so RACINE means SQRT, and PUISSANCE is POWER. I think ASIN, SIN and COS are OK.Hope this helps !Alain

I currently have latitude and longitude expressed in decimal degrees. How do I convert decimal degrees to radians to use your formula. Just multiply by pi/180?I'm glad you mentioned about the French because I don't know if I would have figured that out! Merci!

Yes, just multiply by pi/180 !And just to be complete for my "translation" of the formula from French to English : the decimal comma should become a decimal point.If you want to find useful formulas for navigation purposes, go to this site : http://williams.best.vwh.net/avform.htmGood luck with your calculations !Alain