org.gvsig.fmap.mapcontrol.tools.geo

Class Geo

java.lang.Object

org.gvsig.fmap.mapcontrol.tools.geo.Geo

public class Geo
extends java.lang.Object

Mathematical utilities to work with geographical data:

• Geographical constants:
  • PI / 2.
  • Degrees per radian.
  • Square miles per spherical degree.
  • Square kilometres per spherical degree.
  • Square metres per spherical degree.
• Decimal degrees equivalent to m meters.
• The area of a spherical polygon in spherical degrees, given the latitudes and longitudes of n points, according the Haversine function.

Author:

Vicente Caballero Navarro

Field Summary

Fields

Modifier and Type	Field and Description
static double	Degree Degrees per radian.
static double	HalfPi PI / 2, having PI = 3.14159265358979323846
static double	SqKm Square kilometres per spherical degree.
static double	SqM Square metres per spherical degree.
static double	SqMi Square miles per spherical degree.

Constructor Summary

Constructors

Constructor and Description
Geo()

Method Summary

Modifier and Type	Method and Description
static double	getDecimalDegrees(double m) Gets the decimal degrees equivalent to the m meters.
static double	sphericalPolyArea(double[] lat, double[] lon, int n) Returns the area of a spherical polygon in spherical degrees, given the latitudes and longitudes in lat and lon, respectively.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

Degree

public static double Degree

Degrees per radian.

HalfPi

public static double HalfPi

PI / 2, having PI = 3.14159265358979323846

SqKm

public static double SqKm

Square kilometres per spherical degree.

SqM

public static double SqM

Square metres per spherical degree.

SqMi

public static double SqMi

Square miles per spherical degree.

Constructor Detail

Geo

public Geo()

Method Detail

getDecimalDegrees

public static double getDecimalDegrees(double m)

Gets the decimal degrees equivalent to the m meters.

Uses this formula:
m * R * PI, having R = Radius of the Earth at the equator

Parameters:

m - distance value in meters

Returns:

m * Radius at the equator

sphericalPolyArea

public static double sphericalPolyArea(double[] lat,
                                       double[] lon,
                                       int n)

Returns the area of a spherical polygon in spherical degrees, given the latitudes and longitudes in lat and lon, respectively.

The n data points have indexes which range from 0 to N-1.

Uses the Haversine function for calculating the spherical area of the polygon.

Parameters:

lat - latitude of the vertexes (must be in radians)

lon - longitude of the vertexes (must be in radians)

n - number of vertexes in the polygon

Returns:

the area of a spherical polygon in spherical degrees