Package gov.nasa.worldwind.util.measure

Class AreaMeasurer

  • All Implemented Interfaces:
    MeasurableArea, MeasurableLength
    public class AreaMeasurer
extends LengthMeasurer
implements MeasurableArea
    Utility class to compute approximations of projected and surface (terrain following) area on a globe.

    To properly compute surface area the measurer must be provided with a list of positions that describe a closed path - one which last position is equal to the first.

    Segments which are longer then the current maxSegmentLength will be subdivided along lines following the current pathType - Polyline.LINEAR, Polyline.RHUMB_LINE or Polyline.GREAT_CIRCLE.

    Projected or non terrain following area is computed in a sinusoidal projection which is equivalent or equal area. Surface or terrain following area is approximated by sampling the path bounding sector with square cells along a grid. Cells which center is inside the path have their area estimated and summed according to the overall slope at the cell south-west corner.

    See Also:
    MeasureTool, LengthMeasurer

    • Field Detail

      • surfaceArea

        protected double surfaceArea

      • projectedArea

        protected double projectedArea

    • Constructor Detail

      • AreaMeasurer

        public AreaMeasurer()

      • AreaMeasurer

        public AreaMeasurer​(java.util.ArrayList<? extends Position> positions)

    • Method Detail

      • getAreaTerrainSamplingSteps

        public double getAreaTerrainSamplingSteps()
        Get the sampling grid maximum number of rows or columns for terrain following surface area approximation.
        Returns:
        the sampling grid maximum number of rows or columns.

      • setAreaTerrainSamplingSteps

        public void setAreaTerrainSamplingSteps​(double steps)
        Set the sampling grid maximum number of rows or columns for terrain following surface area approximation.
        Parameters:
        steps - the sampling grid maximum number of rows or columns.
        Throws:
        java.lang.IllegalArgumentException - if steps is less then one.

      • getArea

        public double getArea​(Globe globe)
        Get the surface area approximation for the current path or shape.

        If the measurer is set to follow terrain, the computed area will account for terrain deformations. Otherwise the area is that of the path once projected at sea level - elevation zero.

        Specified by:
        getArea in interface MeasurableArea
        Parameters:
        globe - the globe to draw terrain information from.
        Returns:
        the current shape surface area or -1 if the position list does not describe a closed path or is too short.
        Throws:
        java.lang.IllegalArgumentException - if globe is null.

      • getSurfaceArea

        public double getSurfaceArea​(Globe globe)

      • getProjectedArea

        public double getProjectedArea​(Globe globe)

      • getPerimeter

        public double getPerimeter​(Globe globe)
        Description copied from interface: MeasurableArea
        Returns the length of the object's perimeter in meters. If the object conforms to terrain, the perimeter is that along the terrain, including its hillsides and other undulations.
        Specified by:
        getPerimeter in interface MeasurableArea
        Parameters:
        globe - The globe the object is related to.
        Returns:
        the object's perimeter in meters. Returns -1 if the object does not form an area due to an insufficient number of vertices or any other condition.

      • getWidth

        public double getWidth​(Globe globe)
        Description copied from interface: MeasurableArea
        Returns the longitudinal length of the object in meters. The length is the distance from the object's west-most point to its east-most. If the object is terrain conforming then the
        Specified by:
        getWidth in interface MeasurableArea
        Parameters:
        globe - The globe the object is related to.
        Returns:
        the width of the object in meters.

      • getHeight

        public double getHeight​(Globe globe)
        Description copied from interface: MeasurableArea
        Returns the latitudanl length of the object in meters. The length is the distance from the objects south-most point to its east-most position.
        Specified by:
        getHeight in interface MeasurableArea
        Parameters:
        globe - The globe the object is related to.
        Returns:
        the height of the object in meters.

      • computeProjectedAreaGeometry

        protected double computeProjectedAreaGeometry​(Globe globe)

      • computeTriangleProjectedArea

        protected double computeTriangleProjectedArea​(Globe globe,
                                              float[] verts,
                                              int a,
                                              int b,
                                              int c)

      • computeSurfaceAreaSampling

        protected double computeSurfaceAreaSampling​(Globe globe,
                                            double steps)