Module org.apache.sis.referencing
Package org.apache.sis.referencing.cs

Interface AxisFilter

All Known Implementing Classes:
Axes­Convention
public interface AxisFilter
Modifications to apply on the axes of a coordinate system in order to produce a new coordinate system. Axis­Filter can specify the axes to exclude in the new coordinate system, or specify different units and directions associated to the axes.
Terminology note the word “filter” is understood here as “a computer program or subroutine to process a stream, producing another stream” (Wikipedia).

Note that filtering one or more axes may result in a change of coordinate system type. For example, excluding the z axis of a cylindrical coordinate system results in a polar coordinate system.

Default implementation

All methods in this interface have a default implementation equivalent to no-operation. Implementers need to override only the methods for the aspects to change.

Limitations

This interface is not for changing axis order. For changing axis order in addition to axis directions or units, see Axes­Convention.
Since:
0.6
See Also:

  • Method Details

    • accept

      default boolean accept(CoordinateSystemAxis axis)
      Returns true if the given axis shall be included in the new coordinate system. The default implementation unconditionally returns true.
      Parameters:
      axis - the axis to test.
      Returns:
      true if the given axis shall be included in the new coordinate system.

    • getDirectionReplacement

      default AxisDirection getDirectionReplacement(CoordinateSystemAxis axis, AxisDirection direction)
      Returns a replacement for the given axis direction. The default implementation unconditionally returns the given direction unchanged.

      Example

      For forcing the direction of the z axis toward up while leaving other axes unchanged, one can write: 
          @Override
    public getDirectionReplacement(CoordinateSystemAxis axis, AxisDirection direction) {
        if (direction == AxisDirection.DOWN) {
            direction = AxisDirection.UP;
        }
        return direction;
    }
      Parameters:
      axis - the axis for which to change axis direction, if desired.
      direction - the original axis direction.
      Returns:
      the new axis direction, or direction if there is no change.
      Since:
      0.7

    • getUnitReplacement

      default Unit<?> getUnitReplacement(CoordinateSystemAxis axis, Unit<?> unit)
      Returns a replacement for the given axis unit. The default implementation unconditionally returns the given unit unchanged.

      Example

      For replacing all angular units of a coordinate system to degrees (regardless what the original angular units were) while leaving other kinds of units unchanged, one can write: 
          @Override
    public Unit<?> getUnitReplacement(CoordinateSystemAxis axis, Unit<?> unit) {
        if (Units.isAngular(unit)) {
            unit = Units.DEGREE;
        }
        return unit;
    }
      Parameters:
      axis - the axis for which to change unit, if desired.
      unit - the original axis unit.
      Returns:
      the new axis unit, or unit if there is no change.
      Since:
      0.7