Package com.irurueta.navigation.geodesic

Class PolygonArea

java.lang.Object
com.irurueta.navigation.geodesic.PolygonArea
public class PolygonArea extends Object
Polygon areas. This computes the area of a geodesic polygon using the method given Section 6 of This class lets you add vertices one at a time to the polygon. The area and perimeter are accumulated at two times the standard floating point precision to guard against the loss of accuracy with many-sided polygons. At any point you can ask for the perimeter and area so far. There's an option to treat the points as defining a polyline instead of a polygon; in that case, only the perimeter is computed. Example of use: 
 
 // Compute the area of a geodesic polygon.

 // This program reads lines with lat, lon for each vertex of a polygon.
 // At the end of input, the program prints the number of vertices,
 // the perimeter of the polygon and its area (for the WGS84 ellipsoid).

 import java.util.*;
 import com.irurueta.navigation.geodesic.*;

 public class Planimeter {
   public static void main(String[] args) {
     PolygonArea p = new PolygonArea(Geodesic.WGS84, false);
     try {
       Scanner in = new Scanner(System.in);
       while (true) {
         double lat = in.nextDouble(), lon = in.nextDouble();
         p.AddPoint(lat, lon);
       }
     }
     catch (Exception e) {}
     PolygonResult r = p.Compute();
     System.out.println(r.num + " " + r.perimeter + " " + r.area);
   }
 }

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final double
    area0
     
    private Accumulator
    areasum
     
    private int
    crossings
     
    private final Geodesic
    earth
     
    private double
    lat0
     
    private double
    lat1
     
    private double
    lon0
     
    private double
    lon1
     
    private final int
    mask
     
    private int
    num
     
    private final Accumulator
    perimetersum
     
    private final boolean
    polyline
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    PolygonArea(Geodesic earth, boolean polyline)
    Constructor for PolygonArea.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addEdge(double azi, double s)
    Add an edge to the polygon or polyline.
    void
    addPoint(double lat, double lon)
    Add a point to the polygon or polyline.
    void
    clear()
    Clear PolygonArea, allowing a new polygon to be started.
    PolygonResult
    compute()
    Return the results so far.
    PolygonResult
    compute(boolean reverse, boolean sign)
    Return the results so far.
    Pair
    getCurrentPoint()
    Report the previous vertex added to the polygon or polyline.
    double
    getFlattening()
    Gets the flattening of the ellipsoid.
    double
    getMajorRadius()
    Gets the equatorial radius of the ellipsoid (meters).
    PolygonResult
    testEdge(double azi, double s, boolean reverse, boolean sign)
    Return the results assuming a tentative final test point is added via an azimuth and distance; however, the data for the test point is not saved.
    PolygonResult
    testPoint(double lat, double lon, boolean reverse, boolean sign)
    Return the results assuming a tentative final test point is added; however, the data for the test point is not saved.
    private static int
    transit(double lon1, double lon2)
     
    private static int
    transitDirect(double lon1, double lon2)
     

    Methods inherited from class java.lang.Object

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

  • Field Details

    • earth

      private final Geodesic earth

    • area0

      private final double area0

    • polyline

      private final boolean polyline

    • mask

      private final int mask

    • num

      private int num

    • crossings

      private int crossings

    • areasum

      private Accumulator areasum

    • perimetersum

      private final Accumulator perimetersum

    • lat0

      private double lat0

    • lon0

      private double lon0

    • lat1

      private double lat1

    • lon1

      private double lon1

  • Constructor Details

    • PolygonArea

      public PolygonArea(Geodesic earth, boolean polyline)
      Constructor for PolygonArea.
      Parameters:
      earth - the Geodesic object to use for geodesic calculations.
      polyline - if true that treat the points as defining a polyline instead of a polygon.

  • Method Details

    • clear

      public void clear()
      Clear PolygonArea, allowing a new polygon to be started.

    • addPoint

      public void addPoint(double lat, double lon)
      Add a point to the polygon or polyline. lat should be in the range [−90°, 90°].
      Parameters:
      lat - the latitude of the point (degrees).
      lon - the latitude of the point (degrees).

    • addEdge

      public void addEdge(double azi, double s)
      Add an edge to the polygon or polyline. This does nothing if no points have been added yet. Use PolygonArea.getCurrentPoint to determine the position of the new vertex.
      Parameters:
      azi - azimuth at current point (degrees).
      s - distance from current point to next point (meters).

    • compute

      public PolygonResult compute()
      Return the results so far. Counter-clockwise traversal counts as a positive area.
      Returns:
      PolygonResult(num, perimeter, area) where num is the number of vertices, perimeter is the perimeter of the polygon or the length of the polyline (meters), and area is the area of the polygon (meters2) or Double.NaN of polyline is true in the constructor.

    • compute

      public PolygonResult compute(boolean reverse, boolean sign)
      Return the results so far. More points can be added to the polygon after this call.
      Parameters:
      reverse - if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
      sign - if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
      Returns:
      PolygonResult(num, perimeter, area) where num is the number of vertices, perimeter is the perimeter of the polygon or the length of the polyline (meters), and area is the area of the polygon (meters2) or Double.NaN of polyline is true in the constructor.

    • testPoint

      public PolygonResult testPoint(double lat, double lon, boolean reverse, boolean sign)
      Return the results assuming a tentative final test point is added; however, the data for the test point is not saved. This lets you report a running result for the perimeter and area as the user moves the mouse cursor. Ordinary floating point arithmetic is used to accumulate the data for the test point; thus the area and perimeter returned are less accurate than if addPoint and compute are used. lat should be in the range [−90°, 90°].
      Parameters:
      lat - the latitude of the test point (degrees).
      lon - the longitude of the test point (degrees).
      reverse - if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
      sign - if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
      Returns:
      PolygonResult(num, perimeter, area) where num is the number of vertices, perimeter is the perimeter of the polygon or the length of the polyline (meters), and area is the area of the polygon (meters2) or Double.NaN of polyline is true in the constructor.

    • testEdge

      public PolygonResult testEdge(double azi, double s, boolean reverse, boolean sign)
      Return the results assuming a tentative final test point is added via an azimuth and distance; however, the data for the test point is not saved. This lets you report a running result for the perimeter and area as the user moves the mouse cursor. Ordinary floating point arithmetic is used to accumulate the data for the test point; thus the area and perimeter returned are less accurate than if addPoint and compute are used.
      Parameters:
      azi - azimuth at current point (degrees).
      s - distance from current point to final test point (meters).
      reverse - if true then clockwise (instead of counter-clockwise) traversal counts as a positive area.
      sign - if true then return a signed result for the area if the polygon is traversed in the "wrong" direction instead of returning the area for the rest of the earth.
      Returns:
      PolygonResult(num, perimeter, area) where num is the number of vertices, perimeter is the perimeter of the polygon or the length of the polyline (meters), and area is the area of the polygon (meters2) or Double.NaN of polyline is true in the constructor.

    • getMajorRadius

      public double getMajorRadius()
      Gets the equatorial radius of the ellipsoid (meters).
      Returns:
      a the equatorial radius of the ellipsoid (meters). This is the value inherited from the Geodesic object used in the constructor.

    • getFlattening

      public double getFlattening()
      Gets the flattening of the ellipsoid.
      Returns:
      f the flattening of the ellipsoid. This is the value inherited from the Geodesic object used in the constructor.

    • getCurrentPoint

      public Pair getCurrentPoint()
      Report the previous vertex added to the polygon or polyline. If no points have been added, then Double.NaN is returned. Otherwise, lon will be in the range [−180°, 180°].
      Returns:
      Pair(lat, lon), the current latitude and longitude.

    • transit

      private static int transit(double lon1, double lon2)

    • transitDirect

      private static int transitDirect(double lon1, double lon2)