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PODistance between lat/long points using the haversine formula
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  1. PODistance between lat/long points using the haversine formula
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    copied!<p>I am trying to find the distance between two longitude and latitude points. I am trying ot use the <a href="http://en.wikipedia.org/wiki/Great-circle_distance" rel="nofollow noreferrer">great circle distance</a>. This is the formula: <img src="https://i.stack.imgur.com/3UhsO.png" alt="alt text"></p> <p>I am not sure why but my program is not working. This is the result I am getting: </p> <pre><code>Change Angle: 0.00016244370761414 Earth Radius: 6371 RESULTS: Correct Distance: 24.883 km Computed Distance: 1.0349288612097 </code></pre> <p>Source:</p> <pre><code>$latStart = 44.638; $longStart = -63.587; $latFinish = 44.644; $longFinish = -63.597; # Convert Input to Radians $latStart = deg2Rad($latStart); $longStart = deg2Rad($longStart); $latFinish = deg2Rad($latFinish); $longFinish = deg2Rad($longFinish); # Because the Earth is not perfectly spherical, no single value serves as its # natural radius. Distances from points on the surface to the center range from # 6,353 km to 6,384 km (≈3,947–3,968 mi). Several different ways of modeling the # Earth as a sphere each yield a convenient mean radius of 6371 km (≈3,959 mi). # http://en.wikipedia.org/wiki/Earth_radius $earthRadius = 6371; # difference in Long/Lat $latChange = $latFinish - $latStart; $longChange = $longFinish - $longStart; # haversine formula # numerically stable for small distances # http://en.wikipedia.org/wiki/Great-circle_distance $changeAngle = 2 * asin( sqrt( pow(sin($latChange/2),2) + cos($latStart) * cos($latFinish) * pow(sin($longChange/2),2) ) ); echo "Change Angle: $changeAngle\n"; echo "Earth Radius: $earthRadius\n"; </code></pre>
 

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