/*$************************************************************************************************
 **
 ** $Id: CoordinateSystemAxis.java 831 2006-05-01 00:27:23Z Desruisseaux $
 **
 ** $URL: http://svn.code.sf.net/p/geoapi/code/branches/2.0.x/geoapi/src/main/java/org/opengis/referencing/cs/CoordinateSystemAxis.java $
 **
 ** Copyright (C) 2003-2005 Open GIS Consortium, Inc.
 ** All Rights Reserved. http://www.opengis.org/legal/
 **
 *************************************************************************************************/
package org.opengis.referencing.cs;

// Direct dependencies
import javax.units.Unit;
import org.opengis.referencing.IdentifiedObject;

// Annotations
import org.opengis.annotation.UML;
import static org.opengis.annotation.Obligation.*;
import static org.opengis.annotation.Specification.*;


/**
 * Definition of a coordinate system axis.
 * See axis name constraints.
 *
 * @version Abstract specification 2.0
 * @author ISO/DIS 19111
 * @author Martin Desruisseaux (IRD)
 * @since GeoAPI 1.0
 *
 * @see CoordinateSystem
 * @see Unit
 */
@UML(identifier="CS_CoordinateSystemAxis", specification=ISO_19111)
public interface CoordinateSystemAxis extends IdentifiedObject {
    /**
     * The abbreviation used for this coordinate system axes. This abbreviation is also
     * used to identify the ordinates in coordinate tuple. Examples are "X"
     * and "Y".
     *
     * @return The coordinate system axis abbreviation.
     */
    @UML(identifier="axisAbbrev", obligation=MANDATORY, specification=ISO_19111)
    String getAbbreviation();

    /**
     * Direction of this coordinate system axis. In the case of Cartesian projected
     * coordinates, this is the direction of this coordinate system axis locally.
     * Examples:
     * {@linkplain AxisDirection#NORTH north} or {@linkplain AxisDirection#SOUTH south},
     * {@linkplain AxisDirection#EAST  east}  or {@linkplain AxisDirection#WEST  west},
     * {@linkplain AxisDirection#UP    up}    or {@linkplain AxisDirection#DOWN  down}.
     * Within any set of coordinate system axes, only one of each pair of terms
     * can be used. For earth-fixed coordinate reference systems, this direction is often
     * approximate and intended to provide a human interpretable meaning to the axis. When a
     * geodetic datum is used, the precise directions of the axes may therefore vary slightly
     * from this approximate direction.
     *
     * Note that an {@link org.opengis.referencing.crs.EngineeringCRS} often requires
     * specific descriptions of the directions of its coordinate system axes.
     *
     * @return The coordinate system axis direction.
     */
    @UML(identifier="axisDirection", obligation=MANDATORY, specification=ISO_19111)
    AxisDirection getDirection();

    /**
     * The unit of measure used for this coordinate system axis. The value of this
     * coordinate in a coordinate tuple shall be recorded using this unit of measure,
     * whenever those coordinates use a coordinate reference system that uses a
     * coordinate system that uses this axis.
     *
     * @return  The coordinate system axis unit.
     */
    @UML(identifier="axisUnitID", obligation=MANDATORY, specification=ISO_19111)
    Unit getUnit();
}