gistfile1.js

Math.calculateViewerLength = function(start, end, xPixelRatio, yPixelRatio, minimumX, minimumY) {
	var x1 = (start.x * xPixelRatio) + minimumX
	var y1 = (start.y * yPixelRatio) + minimumY
	var x2 = (end.x * xPixelRatio) + minimumX
	var y2 = (end.y * yPixelRatio) + minimumY

	var majorAxis = 6378137
	var minorAxis = 6356752.3142
	
	//Determines the true angle of the point with respect to the earth
	var trueAnglept1 = (Math.atan(Math.pow(minorAxis, 2) / (Math.pow(majorAxis, 2)) * Math.tan(y1 * Math.PI / 180))) * 180 / Math.PI
	var trueAnglept2 = (Math.atan(Math.pow(minorAxis, 2) / (Math.pow(majorAxis, 2)) * Math.tan(y2 * Math.PI / 180))) * 180 / Math.PI
	
	//Determines the radius of each point to the earth's center
	var radiuspt1 = Math.pow(1/((Math.pow(Math.cos(trueAnglept1 * Math.PI / 180),2)/Math.pow(majorAxis,2)) + (Math.pow(Math.sin(trueAnglept1 * Math.PI / 180),2)/Math.pow(minorAxis,2))),.5) + 334.9
	var radiuspt2 = Math.pow(1/((Math.pow(Math.cos(trueAnglept2 * Math.PI / 180),2)/Math.pow(majorAxis,2)) + (Math.pow(Math.sin(trueAnglept2 * Math.PI / 180),2)/Math.pow(minorAxis,2))),.5) + 334.9
	
	//Determines the x and y coordinates of the each point with respect to the earth
	var xEarthCoorpt1 = radiuspt1 * Math.cos(trueAnglept1 * Math.PI/180)
	var yEarthCoorpt1 = radiuspt1 * Math.sin(trueAnglept1 * Math.PI/180)
	var xEarthCoorpt2 = radiuspt2 * Math.cos(trueAnglept2 * Math.PI/180)
	var yEarthCoorpt2 = radiuspt2 * Math.sin(trueAnglept2 * Math.PI/180)
	
	//Creates a single x and y based on the coordinates above  
	var xCoor = Math.pow(Math.pow((xEarthCoorpt1 - xEarthCoorpt2),2) + Math.pow((yEarthCoorpt1 - yEarthCoorpt2),2),.5)
	var yCoor = 2 * Math.PI * ((((xEarthCoorpt1 + xEarthCoorpt2) / 2)) / 360) * (x1 - x2)
	
	//Computes the distance in feet
	var distance = Math.floor(Math.pow(Math.pow(xCoor,2) + Math.pow(yCoor,2), .5) * 100 + .5) / 100
	distance = Math.floor(ConvertMeters.toFeet(distance) * 100 + .5) / 100;
	return distance;
}