Revision 20098 trunk/libraries/libFMap/src/com/iver/cit/gvsig/fmap/tools/geo/Geo.java
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package com.iver.cit.gvsig.fmap.tools.geo; |
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/** |
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* GeoC is a convenience class used for a couple of things. It can |
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* be used to specifiy constants, and can be used for calculate the geographical area. |
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* <p>Mathematical utilities to work with geographical data: |
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* <ul> |
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* <li>Geographical constants: |
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* <ul> |
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* <li>PI / 2.</li> |
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* <li>Degrees per radian.</li> |
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* <li>Square miles per spherical degree.</li> |
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* <li>Square kilometres per spherical degree.</li> |
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* <li>Square metres per spherical degree.</li> |
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* </ul> |
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* </li> |
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* <li>Decimal degrees equivalent to <i>m</i> meters.</li> |
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* <li>The area of a spherical polygon in spherical degrees, given the latitudes and longitudes |
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* of <i>n</i> points, according the <a href="http://en.wikipedia.org/wiki/Haversine_formula">Haversine function</a>. |
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* </ul> |
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* </p> |
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* |
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* @author Vicente Caballero Navarro |
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*/ |
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public class Geo {
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public static double HalfPi = 1.5707963267948966192313; |
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public static double Degree = 57.295779513082320876798; /* degrees per radian */ |
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public static double SqMi = 273218.4; /* Square mi per spherical degree. */ |
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public static double SqKm = 707632.4; /* Square km per spherical degree. */ |
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public static double SqM = 707632400000.0; /* Square M per spherical degree. */ |
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/** |
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* <i>PI / 2</i>, having PI = 3.14159265358979323846 |
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*/ |
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public static double HalfPi = 1.5707963267948966192313; |
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public static double getDecimalDegrees(double m) {
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/** |
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* Degrees per radian. |
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*/ |
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public static double Degree = 57.295779513082320876798; /* degrees per radian */ |
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/** |
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* Square miles per spherical degree. |
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*/ |
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public static double SqMi = 273218.4; /* Square mi per spherical degree. */ |
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/** |
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* Square kilometres per spherical degree. |
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*/ |
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public static double SqKm = 707632.4; /* Square km per spherical degree. */ |
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/** |
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* Square metres per spherical degree. |
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*/ |
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public static double SqM = 707632400000.0; /* Square M per spherical degree. */ |
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/** |
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* <p>Gets the decimal degrees equivalent to the <i>m</i> meters.</p> |
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* <p>Uses this formula:</br> |
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* <b><i>m * R * PI</i></b>, having R = Radius of the Earth at the equator |
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* </p> |
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* |
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* @param m distance value in meters |
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* |
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* @return <i>m</i> * Radius at the equator |
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*/ |
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public static double getDecimalDegrees(double m) {
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///(m*180)/ (6378137.0 * Math.PI) |
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return (m*8.983152841195214E-6); |
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} |
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/* Haversine function: hav(x)= (1-cos(x))/2. */ |
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private static double hav(double X){
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/** |
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* <p>Operation for calculate the <a href="http://en.wikipedia.org/wiki/Haversine_formula">Haversine function</a>: |
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* <b><i>hav(x)= (1-cos(x))/2</i></b>.</p> |
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* |
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* @param X length between the difference of a coordinate of two points |
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*/ |
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private static double hav(double X){
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return (1.0 - Math.cos(X)) / 2.0; |
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} |
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/* Returns the area of a simple spherical polygon in spherical degrees, |
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given the latitudes and longitudes in Lat and Lon, respectively. |
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The N data points have indices which range from 0 to N-1. |
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This don?t work with multipolygons. |
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*/ |
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/** |
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* <p>Returns the area of a spherical polygon in spherical degrees, |
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* given the latitudes and longitudes in <i>lat</i> and <i>lon</i>, respectively.</p> |
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* |
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* <p>The <i>n</i> data points have indexes which range from 0 to N-1.</p> |
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* |
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* <p>Uses the <a href="http://en.wikipedia.org/wiki/Haversine_formula">Haversine function</a> for calculating the |
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* spherical area of the polygon.</p> |
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* |
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* @param lat latitude of the vertexes <i>(must be in radians)</i> |
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* @param lon longitude of the vertexes <i>(must be in radians)</i> |
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* @param n number of vertexes in the polygon |
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* |
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* @return the area of a spherical polygon in spherical degrees |
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*/ |
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public static double sphericalPolyArea(double[] lat, double[] lon, int n) {
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int j; |
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int k; |
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