001 /*
002 * GeoAPI - Java interfaces for OGC/ISO standards
003 * http://www.geoapi.org
004 *
005 * Copyright (C) 2004-2012 Open Geospatial Consortium, Inc.
006 * All Rights Reserved. http://www.opengeospatial.org/ogc/legal
007 *
008 * Permission to use, copy, and modify this software and its documentation, with
009 * or without modification, for any purpose and without fee or royalty is hereby
010 * granted, provided that you include the following on ALL copies of the software
011 * and documentation or portions thereof, including modifications, that you make:
012 *
013 * 1. The full text of this NOTICE in a location viewable to users of the
014 * redistributed or derivative work.
015 * 2. Notice of any changes or modifications to the OGC files, including the
016 * date changes were made.
017 *
018 * THIS SOFTWARE AND DOCUMENTATION IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE
019 * NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
020 * TO, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT
021 * THE USE OF THE SOFTWARE OR DOCUMENTATION WILL NOT INFRINGE ANY THIRD PARTY
022 * PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS.
023 *
024 * COPYRIGHT HOLDERS WILL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL OR
025 * CONSEQUENTIAL DAMAGES ARISING OUT OF ANY USE OF THE SOFTWARE OR DOCUMENTATION.
026 *
027 * The name and trademarks of copyright holders may NOT be used in advertising or
028 * publicity pertaining to the software without specific, written prior permission.
029 * Title to copyright in this software and any associated documentation will at all
030 * times remain with copyright holders.
031 */
032 package org.opengis.geometry.coordinate;
033
034 import org.opengis.geometry.DirectPosition;
035 import org.opengis.geometry.primitive.Bearing;
036 import org.opengis.annotation.UML;
037
038 import static org.opengis.annotation.Obligation.*;
039 import static org.opengis.annotation.Specification.*;
040
041
042 /**
043 * Arc of the circle determined by 3 points, starting at the first, passing through the second
044 * and terminating at the third. If the 3 points are co-linear, then the arc shall be a 3-point
045 * line string, and will not be able to return values for center, radius, start angle and end
046 * angle.
047 *
048 * <blockquote><font size=2>
049 * <strong>NOTE:</strong> In the model, an {@code Arc} is a subclass of {@link ArcString},
050 * being a trivial arc string consisting of only one arc. This may be counter-intuitive in the
051 * sense that subclasses are often thought of as more complex than their superclass (with
052 * additional methods and attributes). An {@code Arc} is simpler than a {@linkplain ArcString
053 * arc string} in that it has less data, but it is more complex in that it can return geometric
054 * information such as "center", "start angle", and "end angle". This additional computational
055 * complexity forces the subclassing to be the way it is. In addition the "is type of" semantics
056 * works this way and not the other.
057 * </font></blockquote>
058 *
059 * In its simplest representation, the three points in the {@linkplain #getControlPoints control point}
060 * sequence for an {@code Arc} shall consist of, in order, the initial point on the arc, some
061 * point on the arc neither at the start or end, and the end point of the {@code Arc}. If
062 * additional points are given, then all points must lie on the circle defined by any 3 non-colinear
063 * points in the control point array. All points shall lie on the same circle, and shall be given
064 * in the {@linkplain #getControlPoints control point} array in the order in which they occur on
065 * the arc.
066 *
067 * <blockquote><font size=2>
068 * <strong>NOTE:</strong> The use of the term "midPoint" for the center {@linkplain Position position}
069 * of the {@linkplain #getControlPoints control point} sequence is not meant to require that
070 * the {@linkplain Position position} be the geometric midpoint of the arc. This is the best
071 * choice for this {@linkplain Position position} from a computational stability perspective,
072 * but it is not absolutely necessary for the mathematics to work.
073 * </font></blockquote>
074 *
075 * @version <A HREF="http://www.opengeospatial.org/standards/as">ISO 19107</A>
076 * @author Martin Desruisseaux (IRD)
077 * @since GeoAPI 1.0
078 *
079 * @see GeometryFactory#createArc(Position,Position,Position)
080 * @see GeometryFactory#createArc(Position,Position,double,double[])
081 */
082 @UML(identifier="GM_Arc", specification=ISO_19107)
083 public interface Arc extends ArcString {
084 /**
085 * Calculates the center of the circle of which this arc is a portion as a direct position.
086 * The {@linkplain org.opengis.referencing.crs.CoordinateReferenceSystem coordinate reference system}
087 * of the returned {@linkplain DirectPosition direct position} will be the same as that
088 * for this {@code Arc}. In some extreme cases, the {@linkplain DirectPosition direct
089 * position} as calculated may lie outside the domain of validity of the coordinate reference
090 * system used by this {@code Arc} (especially if the underlying arc has a very large
091 * radius). Implementations may choose an appropriate course of action in such cases.
092 *
093 * @return The center of the circle of which this arc is a portion.
094 */
095 @UML(identifier="center", obligation=MANDATORY, specification=ISO_19107)
096 DirectPosition getCenter();
097
098 /**
099 * Calculates the radius of the circle of which this arc is a portion.
100 *
101 * @return The radius of the circle of which this arc is a portion.
102 * @unitof Distance
103 */
104 @UML(identifier="radius", obligation=MANDATORY, specification=ISO_19107)
105 double getRadius();
106
107 /**
108 * Calculates the bearing of the line from the center of the circle of which this arc is a
109 * portion to the start point of the arc. In the 2D case this will be a start angle. In the
110 * 3D case, the normal bearing angle implies that the arc is parallel to the reference circle.
111 * If this is not the case, then the bearing must include altitude information.
112 *
113 * @return The bearing from the {@linkplain #getCenter center} of the circle to the
114 * {@link #getStartPoint start point} of this arc.
115 *
116 * @todo Inconsistent UML: "startAngle" and "startOfArc" are both used.
117 * Which one is the right one?
118 */
119 @UML(identifier="startAngle", obligation=MANDATORY, specification=ISO_19107)
120 Bearing getStartAngle();
121
122 /**
123 * Calculates the bearing of the line from the center of the circle of which this arc is a
124 * portion to the end point of the arc. In the 2D case this will be an end angle. In the 3D
125 * case, the normal bearing angle implies that the arc is parallel to the reference circle.
126 * If this is not the case, then the bearing must include altitude information.
127 *
128 * @return The bearing from the {@linkplain #getCenter center} of the circle to the
129 * {@link #getEndPoint end point} of this arc.
130 *
131 * @todo Inconsistent UML: "endAngle" and "endOfArc" are both used.
132 * Which one is the right one?
133 */
134 @UML(identifier="endAngle", obligation=MANDATORY, specification=ISO_19107)
135 Bearing getEndAngle();
136 }