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POSort latitude and longitude coordinates into clockwise ordered quadrilateral
 

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    <p><strong>Problem</strong></p> <p>Users can provide up to four latitude and longitude coordinates, in any order. They do so with Google Maps. Using Google's <code>Polygon</code> API (v3), the coordinates they select should highlight the selected area between the four coordinates.</p> <p><strong>Question</strong></p> <p>How do you sort an array of latitude and longitude coordinates in (counter-)clockwise order?</p> <p><strong>Solutions and Searches</strong></p> <p><em>StackOverflow Questions</em></p> <ul> <li><a href="https://stackoverflow.com/questions/2353409/drawing-resizable-not-intersecting-polygons">Drawing resizable (not intersecting) polygons</a></li> <li><a href="https://stackoverflow.com/questions/2374708/how-to-sort-points-in-a-google-maps-polygon-so-that-lines-do-not-cross">How to sort points in a Google maps polygon so that lines do not cross?</a></li> <li><a href="https://stackoverflow.com/questions/242404/sort-four-points-in-clockwise-order">Sort Four Points in Clockwise Order</a></li> </ul> <p><em>Related Sites</em></p> <ul> <li><a href="http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm" rel="nofollow noreferrer">http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm</a></li> <li><a href="http://en.literateprograms.org/Quickhull_%28Javascript%29" rel="nofollow noreferrer">http://en.literateprograms.org/Quickhull_%28Javascript%29</a></li> <li><a href="http://www.geocodezip.com/map-markers_ConvexHull_Polygon.asp" rel="nofollow noreferrer">http://www.geocodezip.com/map-markers_ConvexHull_Polygon.asp</a></li> <li><a href="http://softsurfer.com/Archive/algorithm_0103/algorithm_0103.htm" rel="nofollow noreferrer">http://softsurfer.com/Archive/algorithm_0103/algorithm_0103.htm</a></li> </ul> <p><em>Known Algorithms</em></p> <ul> <li>Graham's scan (too complicated)</li> <li>Jarvis March algorithm (handles N points)</li> <li>Recursive Convex Hull (removes a point)</li> </ul> <p><strong>Code</strong></p> <p>Here is what I have so far:</p> <pre><code>// Ensures the markers are sorted: NW, NE, SE, SW function sortMarkers() { var ns = markers.slice( 0 ); var ew = markers.slice( 0 ); ew.sort( function( a, b ) { if( a.position.lat() &lt; b.position.lat() ) { return -1; } else if( a.position.lat() &gt; b.position.lat() ) { return 1; } return 0; }); ns.sort( function( a, b ) { if( a.position.lng() &lt; b.position.lng() ) { return -1; } else if( a.position.lng() &gt; b.position.lng() ) { return 1; } return 0; }); var nw; var ne; var se; var sw; if( ew.indexOf( ns[0] ) &gt; 1 ) { nw = ns[0]; } else { ne = ns[0]; } if( ew.indexOf( ns[1] ) &gt; 1 ) { nw = ns[1]; } else { ne = ns[1]; } if( ew.indexOf( ns[2] ) &gt; 1 ) { sw = ns[2]; } else { se = ns[2]; } if( ew.indexOf( ns[3] ) &gt; 1 ) { sw = ns[3]; } else { se = ns[3]; } markers[0] = nw; markers[1] = ne; markers[2] = se; markers[3] = sw; } </code></pre> <p>Thank you.</p>
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    1. COWhy not use the solution chosen in the SO question you referenced within the question? It sounds like the same problem.
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      1. USDaniel Beardsley
    2. CO@Dave, not quite sure what you're looking for. How would the following points be sorted: `a=(1,1)`, `b=(2,4)`, `c=(3,3)`, `d=(6,2)`? Like `[b,d,c,a]` perhaps? Or do you want to exclude `c` from the sorted array to make the polygon convex?
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      1. USBart Kiers
    3. CO@Dave, I assume you realize that the convex hull of a set of points larger than 3, might exclude 1 point. In your code snippet I don't see you taking that into account, yet you make references to Convex Hull algorithms...
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