Notes on Calculating distance: (this is a placeholder-if you actually see this, and it is more then a few weeks after today, please email rich@testingrange.com and tell him to get off his duff 1/26/2005) 1. show how to use pythagorean...but how it is bogus on a curve. 2. show the cosine improved pythagorean calculation-it is actually pretty good.. 3. show a table of discrepencies. It is not much for a degree...like 6 hundredths of a mile. and then show the * cos( (lat2-lat1/2) ) trickand then instead of 'Worse' say 'this is better, but over distances greater then 20 km or so.. at our latitude, one degree north and one degree west (ie a diagnol) is great circle 87.83 miles, cos improved pythagorean is 87.89 - an accuracy totally worth the two fewer deg2rad and 5 fewer trig functions (acos, cos, sin, sin, cos) - 1 cos and a sqrt versus 5 trigs...well, maybe it isn't faster, but certainly much easier to remember for me. add 'radius of the earth in miles' in google...