/*
 * GIS.java
 *
 * Created on March 4, 2001, 8:41 AM
 */

package myutil;

/**
 *
 * @author  rvdb
 * @version
 */
public class GIS extends Object {

    /** Creates new GIS */
    public GIS() {
    }

    public static void setCenter(double lat, double lon) {
        double phi   = 2*Math.PI*(90-lat)/360;
        double theta = 2*Math.PI*lon/360;

        /****************************************************
         * Compute unit tangent vector parallel to lat line.
         ***************************************************/

        x1 = -Math.sin(theta);
        y1 =  Math.cos(theta);
        z1 =  0;

        /****************************************************
         * Compute unit tangent vector parallel to lon line.
         ***************************************************/

        x2 = -Math.cos(phi)*Math.cos(theta);
        y2 = -Math.cos(phi)*Math.sin(theta);
        z2 =  Math.sin(phi);
    }

    public static double azimuthX(double lat, double lon)
    {

        /****************************************************
         * The azimuthal coords are simply the inner products
         * of the cartesian coords with these unit vectors.
         ***************************************************/

        double phi   = 2*Math.PI*(90-lat)/360;
        double theta = 2*Math.PI*lon/360;

        double xbar = Math.sin(phi)*Math.cos(theta);
        double ybar = Math.sin(phi)*Math.sin(theta);
        double zbar = Math.cos(phi);

        return xbar*x1 + ybar*y1 + zbar*z1;
    }
    public static double azimuthY(double lat, double lon)
    {

        /****************************************************
         * The azimuthal coords are simply the inner products
         * of the cartesian coords with these unit vectors.
         ***************************************************/

        double phi   = 2*Math.PI*(90-lat)/360;
        double theta = 2*Math.PI*lon/360;

        double xbar = Math.sin(phi)*Math.cos(theta);
        double ybar = Math.sin(phi)*Math.sin(theta);
        double zbar = Math.cos(phi);

        return xbar*x2 + ybar*y2 + zbar*z2;
    }

    static double x1, y1, z1, x2, y2, z2;

}