89 lines
2.6 KiB
Java
89 lines
2.6 KiB
Java
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package geography;
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/**
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* An abstract class that is extended to construct different types
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* map projections.
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*
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* @author Prof. David Bernstein, James Madison University
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* @version 1.0
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*/
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public abstract class AbstractMapProjection implements MapProjection
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{
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// Radius of spherical Earth (in km)
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protected static final double R = 6369.0;
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protected static final double PI = Math.PI;
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protected static final double TWO_PI = 2.0*Math.PI;
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protected static final double PI_OVER_TWO = Math.PI/2.0;
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protected static final double PI_OVER_FOUR = Math.PI/4.0;
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protected static final double RADIANS_PER_DEGREE = 2.0*Math.PI/360.0;
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protected static final double DEGREES_PER_RADIAN = 1.0 / RADIANS_PER_DEGREE;
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/**
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* The forward transformation (i.e., from Longitude/Latitude in
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* __degrees__ to kilometers above the equator and to the west of the
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* reference meridian).
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*
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* @param ll The longitude and latitude in __degrees__ (in that order)
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* @return KMs west of reference and north of equator (in that order)
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*/
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@Override
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public double[] forward(final double[] ll)
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{
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double lambda = ll[0] * RADIANS_PER_DEGREE;
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double phi = ll[1] * RADIANS_PER_DEGREE;
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return forward(lambda, phi);
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}
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/**
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* The forward transformation (i.e., from Longitude/Latitude in
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* __radians__ to kilometers above the equator and to the west of the
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* reference meridian).
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*
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* @param lambda The longitude in __radians__
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* @param phi The latitude in __radians__
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* @return KMs west of reference and north of equator (in that order)
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*/
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@Override
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public abstract double[] forward(final double lambda, final double phi);
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/**
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* The inverse transformation from kilometers (above the
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* equator and to the west of the reference meridian)
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* to Longitude/Latitude in __degrees__.
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*
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* @param km The point in above,west coordinates (in that order)
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* @return The longitude and latitude in __degrees__ (in that order)
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*/
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@Override
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public double[] inverse(final double[] km)
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{
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double[] ll = inverse(km[0], km[1]);// In radians
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ll[0] = ll[0] * DEGREES_PER_RADIAN; // In degrees
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ll[1] = ll[1] * DEGREES_PER_RADIAN; // In degrees
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return ll;
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}
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/**
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* The inverse transformation from kilometers (above the
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* equator and to the west of the reference meridian)
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* to Longitude/Latitude in __radians__.
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*
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* @param ew The distance east/west in kilometers
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* @param ns The distance north/south in kilometers
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* @return The longitude and latitude in __radians__ (in that order)
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*/
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@Override
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public abstract double[] inverse(final double ew, final double ns);
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}
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