墨卡托投影、地理坐标系、地面分辨率、地图比例尺

using System;

using System.Text;

namespace Microsoft.MapPoint

{

    static class TileSystem

    {

        private const double EarthRadius = 6378137;

        private const double MinLatitude = -85.05112878;

        private const double MaxLatitude = 85.05112878;

        private const double MinLongitude = -180;

        private const double MaxLongitude = 180;

        /// <summary>

        /// Clips a number to the specified minimum and maximum values.

        /// </summary>

        /// <param name="n">The number to clip.</param>

        /// <param name="minValue">Minimum allowable value.</param>

        /// <param name="maxValue">Maximum allowable value.</param>

        /// <returns>The clipped value.</returns>

        private static double Clip(double n, double minValue, double maxValue)

        {

            return Math.Min(Math.Max(n, minValue), maxValue);

        }

        /// <summary>

        ///Determines the map width and height (in pixels) at a specified level

        /// of detail.

        /// </summary>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <returns>The map width and height in pixels.</returns>

        public static uint MapSize(intlevelOfDetail)

        {

            return (uint) 256 << levelOfDetail;

        }

        /// <summary>

        ///Determines the ground resolution (in meters per pixel) at a specified

        /// latitude and level of detail.

        /// </summary>

        /// <param name="latitude">Latitude (in degrees) at which to measure the

        /// ground resolution.</param>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <returns>The ground resolution, in meters per pixel.</returns>

        public static double GroundResolution(double latitude, int levelOfDetail)

        {

            latitude = Clip(latitude, MinLatitude, MaxLatitude);

            return Math.Cos(latitude * Math.PI / 180) * 2 * Math.PI * EarthRadius / MapSize(levelOfDetail);

        }

        /// <summary>

        ///Determines the map scale at a specified latitude, level of detail,

        /// and screen resolution.

        /// </summary>

        /// <param name="latitude">Latitude (in degrees) at which to measure the

        /// map scale.</param>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <param name="screenDpi">Resolution of the screen, in dots per inch.</param>

        /// <returns>The map scale, expressed as the denominator N of the ratio 1 : N.</returns>

        public static double MapScale(double latitude, int levelOfDetail, intscreenDpi)

        {

            return GroundResolution(latitude, levelOfDetail) * screenDpi / 0.0254;

        }

        /// <summary>

        /// Converts a point from latitude/longitude WGS-84 coordinates (in degrees)

        /// into pixel XY coordinates at a specified level of detail.

        /// </summary>

        /// <param name="latitude">Latitude of the point, in degrees.</param>

        /// <param name="longitude">Longitude of the point, in degrees.</param>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <param name="pixelX">Output parameter receiving the X coordinate in pixels.</param>

        /// <param name="pixelY">Output parameter receiving the Y coordinate in pixels.</param>

        public static void LatLongToPixelXY(double latitude, double longitude, intlevelOfDetail, out int pixelX, out int pixelY)

        {

            latitude = Clip(latitude, MinLatitude, MaxLatitude);

            longitude = Clip(longitude, MinLongitude, MaxLongitude);

            double x = (longitude + 180) / 360; 

            double sinLatitude = Math.Sin(latitude * Math.PI / 180);

            double y = 0.5 - Math.Log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);

            uint mapSize = MapSize(levelOfDetail);

            pixelX = (int) Clip(x * mapSize + 0.5, 0, mapSize - 1);

            pixelY = (int) Clip(y * mapSize + 0.5, 0, mapSize - 1);

        }

        /// <summary>

        /// Converts a pixel from pixel XY coordinates at a specified level of detail

        /// into latitude/longitude WGS-84 coordinates (in degrees).

        /// </summary>

        /// <param name="pixelX">X coordinate of the point, in pixels.</param>

        /// <param name="pixelY">Y coordinates of the point, in pixels.</param>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <param name="latitude">Output parameter receiving the latitude in degrees.</param>

        /// <param name="longitude">Output parameter receiving the longitude in degrees.</param>

        public static void PixelXYToLatLong(int pixelX, int pixelY, intlevelOfDetail, out double latitude, out double longitude)

        {

            double mapSize = MapSize(levelOfDetail);

            double x = (Clip(pixelX, 0, mapSize - 1) / mapSize) - 0.5;

            double y = 0.5 - (Clip(pixelY, 0, mapSize - 1) / mapSize);

            latitude = 90 - 360 * Math.Atan(Math.Exp(-y * 2 * Math.PI)) / Math.PI;

            longitude = 360 * x;

        }

        /// <summary>

        /// Converts pixel XY coordinates into tile XY coordinates of the tile containing

        /// the specified pixel.

        /// </summary>

        /// <param name="pixelX">Pixel X coordinate.</param>

        /// <param name="pixelY">Pixel Y coordinate.</param>

        /// <param name="tileX">Output parameter receiving the tile X coordinate.</param>

        /// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>

        public static void PixelXYToTileXY(int pixelX, int pixelY, out int tileX, out int tileY)

        {

            tileX = pixelX / 256;

            tileY = pixelY / 256;

        }

        /// <summary>

        /// Converts tile XY coordinates into pixel XY coordinates of the upper-left pixel

        /// of the specified tile.

        /// </summary>

        /// <param name="tileX">Tile X coordinate.</param>

        /// <param name="tileY">Tile Y coordinate.</param>

        /// <param name="pixelX">Output parameter receiving the pixel X coordinate.</param>

        /// <param name="pixelY">Output parameter receiving the pixel Y coordinate.</param>

        public static void TileXYToPixelXY(int tileX, int tileY, out int pixelX, out int pixelY)

        {

            pixelX = tileX * 256;

            pixelY = tileY * 256;

        }

        /// <summary>

        /// Converts tile XY coordinates into a QuadKey at a specified level of detail.

        /// </summary>

        /// <param name="tileX">Tile X coordinate.</param>

        /// <param name="tileY">Tile Y coordinate.</param>

        /// <param name="levelOfDetail">Level of detail, from 1 (lowest detail)

        /// to 23 (highest detail).</param>

        /// <returns>A string containing the QuadKey.</returns>

        public static string TileXYToQuadKey(int tileX, int tileY, intlevelOfDetail)

        {

            StringBuilder quadKey = newStringBuilder();

            for (int i = levelOfDetail; i > 0; i--)

            {

                char digit = ‘0‘;

                int mask = 1 << (i - 1);

                if ((tileX & mask) != 0)

                {

                    digit++;

                }

                if ((tileY & mask) != 0)

                {

                    digit++;

                    digit++;

                }

                quadKey.Append(digit);

            }

            return quadKey.ToString();

        }

        /// <summary>

        /// Converts a QuadKey into tile XY coordinates.

        /// </summary>

        /// <param name="quadKey">QuadKey of the tile.</param>

        /// <param name="tileX">Output parameter receiving the tile X coordinate.</param>

        /// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>

        /// <param name="levelOfDetail">Output parameter receiving the level of detail.</param>

        public static void QuadKeyToTileXY(string quadKey, out int tileX, out int tileY, out intlevelOfDetail)

        {

            tileX = tileY = 0;

            levelOfDetail = quadKey.Length;

            for (int i = levelOfDetail; i > 0; i--)

            {

                int mask = 1 << (i - 1);

                switch (quadKey[levelOfDetail - i])

                {

                    case ‘0‘:

                        break;

                    case ‘1‘:

                        tileX |= mask;

                        break;

                    case ‘2‘:

                        tileY |= mask;

                        break;

                    case ‘3‘:

                        tileX |= mask;

                        tileY |= mask;

                        break;

                    default:

                        throw new ArgumentException("Invalid QuadKey digit sequence.");

                }

            }

        }

    }

}