openlayers/lib/OpenLayers/Geometry/Curve.js

   1 /* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
   2  * license.  See http://svn.openlayers.org/trunk/openlayers/license.txt for the
   3  * full text of the license. */
   4
   5 /**
   6  * @requires OpenLayers/Geometry/MultiPoint.js
   7  */
   8
   9 /**
  10  * Class: OpenLayers.Geometry.Curve
  11  * A Curve is a MultiPoint, whose points are assumed to be connected. To
  12  * this end, we provide a "getLength()" function, which iterates through
  13  * the points, summing the distances between them.
  14  *
  15  * Inherits:
  16  *  - <OpenLayers.Geometry.MultiPoint>
  17  */
  18 OpenLayers.Geometry.Curve = OpenLayers.Class(OpenLayers.Geometry.MultiPoint, {
  19
  20     /**
  21      * Property: componentTypes
  22      * {Array(String)} An array of class names representing the types of
  23      *                 components that the collection can include.  A null
  24      *                 value means the component types are not restricted.
  25      */
  26     componentTypes: ["OpenLayers.Geometry.Point"],
  27
  28     /**
  29      * Constructor: OpenLayers.Geometry.Curve
  30      *
  31      * Parameters:
  32      * point - {Array(<OpenLayers.Geometry.Point>)}
  33      */
  34     initialize: function(points) {
  35         OpenLayers.Geometry.MultiPoint.prototype.initialize.apply(this,
  36                                                                   arguments);
  37     },
  38
  39     /**
  40      * APIMethod: getLength
  41      *
  42      * Returns:
  43      * {Float} The length of the curve
  44      */
  45     getLength: function() {
  46         var length = 0.0;
  47         if ( this.components && (this.components.length > 1)) {
  48             for(var i=1, len=this.components.length; i<len; i++) {
  49                 length += this.components[i-1].distanceTo(this.components[i]);
  50             }
  51         }
  52         return length;
  53     },
  54
  55     /**
  56      * APIMethod: getGeodesicLength
  57      * Calculate the approximate length of the geometry were it projected onto
  58      *     the earth.
  59      *
  60      * projection - {<OpenLayers.Projection>} The spatial reference system
  61      *     for the geometry coordinates.  If not provided, Geographic/WGS84 is
  62      *     assumed.
  63      *
  64      * Returns:
  65      * {Float} The appoximate geodesic length of the geometry in meters.
  66      */
  67     getGeodesicLength: function(projection) {
  68         var geom = this;  // so we can work with a clone if needed
  69         if(projection) {
  70             var gg = new OpenLayers.Projection("EPSG:4326");
  71             if(!gg.equals(projection)) {
  72                 geom = this.clone().transform(projection, gg);
  73             }
  74         }
  75         var length = 0.0;
  76         if(geom.components && (geom.components.length > 1)) {
  77             var p1, p2;
  78             for(var i=1, len=geom.components.length; i<len; i++) {
  79                 p1 = geom.components[i-1];
  80                 p2 = geom.components[i];
  81                 // this returns km and requires lon/lat properties
  82                 length += OpenLayers.Util.distVincenty(
  83                     {lon: p1.x, lat: p1.y}, {lon: p2.x, lat: p2.y}
  84                 );
  85             }
  86         }
  87         // convert to m
  88         return length * 1000;
  89     },
  90
  91     CLASS_NAME: "OpenLayers.Geometry.Curve"
  92 });