Example usage for org.apache.commons.math.util FastMath acos

Introduction

In this page you can find the example usage for org.apache.commons.math.util FastMath acos.

Prototype

public static double acos(double x) 

Source Link

Document

Compute the arc cosine of a number.

Usage

From source file:org.esa.nest.gpf.ALOSDeskewingOp.java

private boolean getLook(final stateVector v, final double slant, final double yaw, final double[] plook) {

    final GeoCoding geoCoding = sourceProduct.getGeoCoding();
    if (geoCoding == null) {
        throw new OperatorException("GeoCoding is null");
    }/*w w w.j a va  2 s.c  o  m*/

    final GeoPos geoPos = geoCoding.getGeoPos(new PixelPos(0, 0), null);
    final double earthRadius = computeEarthRadius(geoPos);

    final double ht = Math.sqrt(v.xPos * v.xPos + v.yPos * v.yPos + v.zPos * v.zPos);

    double look = FastMath.acos((ht * ht + slant * slant - earthRadius * earthRadius) / (2.0 * slant * ht));

    for (int iter = 0; iter < 100; iter++) {

        double delta_range = slant - calcRange(v, look, yaw);
        if (Math.abs(delta_range) < 0.1) {
            plook[0] = look;
            return true;
        } else {
            double sininc = (ht / earthRadius) * FastMath.sin(look);
            double taninc = sininc / Math.sqrt(1 - sininc * sininc);
            look += delta_range / (slant * taninc);
        }
    }

    return false;
}

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From source file:org.esa.nest.gpf.SARSimulationOp.java

/**
 * Compute elevation angle (in degree)./* www  .j  a  va 2s.co m*/
 * @param slantRange The slant range.
 * @param earthPoint The coordinate for target on earth surface.
 * @param sensorPos The coordinate for satellite position.
 * @return The elevation angle in degree.
 */
private static double computeElevationAngle(final double slantRange, final double[] earthPoint,
        final double[] sensorPos) {

    final double H2 = sensorPos[0] * sensorPos[0] + sensorPos[1] * sensorPos[1] + sensorPos[2] * sensorPos[2];
    final double R2 = earthPoint[0] * earthPoint[0] + earthPoint[1] * earthPoint[1]
            + earthPoint[2] * earthPoint[2];

    return FastMath.acos((slantRange * slantRange + H2 - R2) / (2 * slantRange * Math.sqrt(H2)))
            * org.esa.beam.util.math.MathUtils.RTOD;
}

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