coordinatesystem.cs

Sharp Map 用于制作GIS系统S harp Map 用于制作GIS系统S harp Map 用于制作GIS系统

// Copyright 2005, 2006 - Morten Nielsen (www.iter.dk)
//
// This file is part of SharpMap.
// SharpMap is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
// 
// SharpMap is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public License
// along with SharpMap; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

using System;
using System.Collections.Generic;
using System.Text;

namespace SharpMap.CoordinateSystems
{
	/// <summary>
	/// Base interface for all coordinate systems.
	/// </summary>
	/// <remarks>
	/// <para>A coordinate system is a mathematical space, where the elements of the space
	/// are called positions. Each position is described by a list of numbers. The length 
	/// of the list corresponds to the dimension of the coordinate system. So in a 2D 
	/// coordinate system each position is described by a list containing 2 numbers.</para>
	/// <para>However, in a coordinate system, not all lists of numbers correspond to a 
	/// position - some lists may be outside the domain of the coordinate system. For 
	/// example, in a 2D Lat/Lon coordinate system, the list (91,91) does not correspond
	/// to a position.</para>
	/// <para>Some coordinate systems also have a mapping from the mathematical space into 
	/// locations in the real world. So in a Lat/Lon coordinate system, the mathematical 
	/// position (lat, long) corresponds to a location on the surface of the Earth. This 
	/// mapping from the mathematical space into real-world locations is called a Datum.</para>
	/// </remarks>		
	public abstract class CoordinateSystem : Info, ICoordinateSystem
	{
		/// <summary>
		/// Initializes a new instance of a coordinate system.
		/// </summary>
		/// <param name="name">Name</param>
		/// <param name="authority">Authority name</param>
		/// <param name="authorityCode">Authority-specific identification code.</param>
		/// <param name="alias">Alias</param>
		/// <param name="abbreviation">Abbreviation</param>
		/// <param name="remarks">Provider-supplied remarks</param>
		internal CoordinateSystem(string name, string authority, long authorityCode, string alias, string abbreviation, string remarks)
			: base (name,authority,authorityCode,alias,abbreviation,remarks)
		{
		}
		#region ICoordinateSystem Members

		/// <summary>
		/// Dimension of the coordinate system.
		/// </summary>
		public int Dimension
		{
			get { return _AxisInfo.Count; }
		}

		/// <summary>
		/// Gets the units for the dimension within coordinate system. 
		/// Each dimension in the coordinate system has corresponding units.
		/// </summary>
		public abstract IUnit GetUnits(int dimension);

		private List<AxisInfo> _AxisInfo;
		internal List<AxisInfo> AxisInfo
		{
			get { return _AxisInfo; }
			set { _AxisInfo = value; }
		}


		/// <summary>
		/// Gets axis details for dimension within coordinate system.
		/// </summary>
		/// <param name="dimension">Dimension</param>
		/// <returns>Axis info</returns>
		public AxisInfo GetAxis(int dimension)
		{
			if (dimension >= _AxisInfo.Count || dimension < 0)
				throw new ArgumentException("AxisInfo not available for dimension " + dimension.ToString());
			return _AxisInfo[dimension];
		}
				

		private SharpMap.Geometries.BoundingBox _DefaultEnvelope;

		/// <summary>
		/// Gets default envelope of coordinate system.
		/// </summary>
		/// <remarks>
		/// Coordinate systems which are bounded should return the minimum bounding box of their domain. 
		/// Unbounded coordinate systems should return a box which is as large as is likely to be used. 
		/// For example, a (lon,lat) geographic coordinate system in degrees should return a box from 
		/// (-180,-90) to (180,90), and a geocentric coordinate system could return a box from (-r,-r,-r)
		/// to (+r,+r,+r) where r is the approximate radius of the Earth.
		/// </remarks>
		public SharpMap.Geometries.BoundingBox DefaultEnvelope
		{
			get { return _DefaultEnvelope; }
			set { _DefaultEnvelope = value; }
		}

		#endregion
	}
}