Created
September 11, 2012 11:36
-
-
Save vectoroc/3697755 to your computer and use it in GitHub Desktop.
Port of GlobalMercator from python to php
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| <?php | |
| ############################################################################### | |
| # Project: GDAL2Tiles, Google Summer of Code 2007 & 2008 | |
| # Global Map Tiles Classes | |
| # Purpose: Convert a raster into TMS tiles, create KML SuperOverlay EPSG:4326, | |
| # generate a simple HTML viewers based on Google Maps and OpenLayers | |
| # Author: Klokan Petr Pridal, klokan at klokan dot cz | |
| # Web: http://www.klokan.cz/projects/gdal2tiles/ | |
| # | |
| ############################################################################### | |
| # Copyright (c) 2008 Klokan Petr Pridal. All rights reserved. | |
| # | |
| # Permission is hereby granted, free of charge, to any person obtaining a | |
| # copy of this software and associated documentation files (the "Software"), | |
| # to deal in the Software without restriction, including without limitation | |
| # the rights to use, copy, modify, merge, publish, distribute, sublicense, | |
| # and/or sell copies of the Software, and to permit persons to whom the | |
| # Software is furnished to do so, subject to the following conditions: | |
| # | |
| # The above copyright notice and this permission notice shall be included | |
| # in all copies or substantial portions of the Software. | |
| # | |
| # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS | |
| # OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
| # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | |
| # THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
| # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | |
| # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | |
| # DEALINGS IN THE SOFTWARE. | |
| ############################################################################### | |
| /** | |
| """ | |
| TMS Global Mercator Profile | |
| --------------------------- | |
| Functions necessary for generation of tiles in Spherical Mercator projection, | |
| EPSG:900913 (EPSG:gOOglE, Google Maps Global Mercator), EPSG:3785, OSGEO:41001. | |
| Such tiles are compatible with Google Maps, Microsoft Virtual Earth, Yahoo Maps, | |
| UK Ordnance Survey OpenSpace API, ... | |
| and you can overlay them on top of base maps of those web mapping applications. | |
| Pixel and tile coordinates are in TMS notation (origin [0,0] in bottom-left). | |
| What coordinate conversions do we need for TMS Global Mercator tiles:: | |
| LatLon <-> Meters <-> Pixels <-> Tile | |
| WGS84 coordinates Spherical Mercator Pixels in pyramid Tiles in pyramid | |
| lat/lon XY in metres XY pixels Z zoom XYZ from TMS | |
| EPSG:4326 EPSG:900913 | |
| .----. --------- -- TMS | |
| \ / | | /--------/ QuadTree | |
| ----- --------- /------------/ | |
| KML, public WebMapService Web Clients TileMapService | |
| What is the coordinate extent of Earth in EPSG:900913? | |
| [-20037508.342789244, -20037508.342789244, 20037508.342789244, 20037508.342789244] | |
| Constant 20037508.342789244 comes from the circumference of the Earth in meters, | |
| which is 40 thousand kilometers, the coordinate origin is in the middle of extent. | |
| In fact you can calculate the constant as: 2 * math.pi * 6378137 / 2.0 | |
| $ echo 180 85 | gdaltransform -s_srs EPSG:4326 -t_srs EPSG:900913 | |
| Polar areas with abs(latitude) bigger then 85.05112878 are clipped off. | |
| What are zoom level constants (pixels/meter) for pyramid with EPSG:900913? | |
| whole region is on top of pyramid (zoom=0) covered by 256x256 pixels tile, | |
| every lower zoom level resolution is always divided by two | |
| initialResolution = 20037508.342789244 * 2 / 256 = 156543.03392804062 | |
| What is the difference between TMS and Google Maps/QuadTree tile name convention? | |
| The tile raster itself is the same (equal extent, projection, pixel size), | |
| there is just different identification of the same raster tile. | |
| Tiles in TMS are counted from [0,0] in the bottom-left corner, id is XYZ. | |
| Google placed the origin [0,0] to the top-left corner, reference is XYZ. | |
| Microsoft is referencing tiles by a QuadTree name, defined on the website: | |
| http://msdn2.microsoft.com/en-us/library/bb259689.aspx | |
| The lat/lon coordinates are using WGS84 datum, yeh? | |
| Yes, all lat/lon we are mentioning should use WGS84 Geodetic Datum. | |
| Well, the web clients like Google Maps are projecting those coordinates by | |
| Spherical Mercator, so in fact lat/lon coordinates on sphere are treated as if | |
| the were on the WGS84 ellipsoid. | |
| From MSDN documentation: | |
| To simplify the calculations, we use the spherical form of projection, not | |
| the ellipsoidal form. Since the projection is used only for map display, | |
| and not for displaying numeric coordinates, we don't need the extra precision | |
| of an ellipsoidal projection. The spherical projection causes approximately | |
| 0.33 percent scale distortion in the Y direction, which is not visually noticable. | |
| How do I create a raster in EPSG:900913 and convert coordinates with PROJ.4? | |
| You can use standard GIS tools like gdalwarp, cs2cs or gdaltransform. | |
| All of the tools supports -t_srs 'epsg:900913'. | |
| For other GIS programs check the exact definition of the projection: | |
| More info at http://spatialreference.org/ref/user/google-projection/ | |
| The same projection is degined as EPSG:3785. WKT definition is in the official | |
| EPSG database. | |
| Proj4 Text: | |
| +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 | |
| +k=1.0 +units=m +nadgrids=@null +no_defs | |
| Human readable WKT format of EPGS:900913: | |
| PROJCS["Google Maps Global Mercator", | |
| GEOGCS["WGS 84", | |
| DATUM["WGS_1984", | |
| SPHEROID["WGS 84",6378137,298.2572235630016, | |
| AUTHORITY["EPSG","7030"]], | |
| AUTHORITY["EPSG","6326"]], | |
| PRIMEM["Greenwich",0], | |
| UNIT["degree",0.0174532925199433], | |
| AUTHORITY["EPSG","4326"]], | |
| PROJECTION["Mercator_1SP"], | |
| PARAMETER["central_meridian",0], | |
| PARAMETER["scale_factor",1], | |
| PARAMETER["false_easting",0], | |
| PARAMETER["false_northing",0], | |
| UNIT["metre",1, | |
| AUTHORITY["EPSG","9001"]]] | |
| """ | |
| **/ | |
| class GlobalMercator { | |
| function __construct($tileSize = 256) { | |
| $this->tileSize = $tileSize; | |
| $this->initialResolution = 2 * pi() * 6378137 / $this->tileSize; | |
| # 156543.03392804062 for tileSize 256 pixels | |
| $this->originShift = 2 * pi() * 6378137 / 2.0; | |
| # 20037508.342789244 | |
| } | |
| /** | |
| * Converts given lat/lon in WGS84 Datum to XY in Spherical Mercator EPSG:900913 | |
| * @param $lat | |
| * @param $lon | |
| * @return array | |
| */ | |
| function LatLonToMeters($lat, $lon) { | |
| $mx = $lon * $this->originShift / 180.0; | |
| $my = log(tan((90 +$lat) * pi() / 360.0 )) / (pi() / 180.0); | |
| $my = $my * $this->originShift / 180.0; | |
| return array($mx, $my); | |
| } | |
| /** | |
| * Converts XY point from Spherical Mercator EPSG:900913 to lat/lon in WGS84 Datum | |
| * @param $mx | |
| * @param $my | |
| * @return array | |
| */ | |
| function MetersToLatLon($mx, $my) { | |
| $lon = ($mx / $this->originShift) * 180.0; | |
| $lat = ($my / $this->originShift) * 180.0; | |
| $lat = 180 / pi() * (2 * atan( exp( $lat * pi() / 180.0)) - pi() / 2.0); | |
| return array($lat, $lon); | |
| } | |
| /** | |
| * Converts pixel coordinates in given zoom level of pyramid to EPSG:900913 | |
| * @param $px | |
| * @param $py | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function PixelsToMeters($px, $py, $zoom) { | |
| $res = $this->Resolution( $zoom ); | |
| $mx = $px * $res - $this->originShift; | |
| $my = $py * $res - $this->originShift; | |
| return array($mx, $my); | |
| } | |
| /** | |
| * Converts EPSG:900913 to pyramid pixel coordinates in given zoom level | |
| * @param $mx | |
| * @param $my | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function MetersToPixels($mx, $my, $zoom) { | |
| $res = $this->Resolution( $zoom ); | |
| $px = ($mx + $this->originShift) / $res; | |
| $py = ($my + $this->originShift) / $res; | |
| return array($px, $py); | |
| } | |
| /** | |
| * Returns a tile covering region in given pixel coordinates | |
| * @param $px | |
| * @param $py | |
| * @return array | |
| */ | |
| function PixelsToTile($px, $py) { | |
| $tx = intval( ceil( $px / floatval($this->tileSize) ) - 1 ); | |
| $ty = intval( ceil( $py / floatval($this->tileSize) ) - 1 ); | |
| return array($tx, $ty); | |
| } | |
| /** | |
| * Move the origin of pixel coordinates to top-left corner | |
| * @param $px | |
| * @param $py | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function PixelsToRaster($px, $py, $zoom) { | |
| $mapSize = $this->tileSize << $zoom; | |
| return array($px, $mapSize - $py); | |
| } | |
| /** | |
| * Returns tile for given mercator coordinates | |
| * @param $mx | |
| * @param $my | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function MetersToTile($mx, $my, $zoom) { | |
| list($px, $py) = $this->MetersToPixels( $mx, $my, $zoom); | |
| return $this->PixelsToTile( $px, $py); | |
| } | |
| /** | |
| * Returns bounds of the given tile in EPSG:900913 coordinates | |
| * @param $tx | |
| * @param $ty | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function TileBounds($tx, $ty, $zoom) { | |
| list($minx, $miny) = $this->PixelsToMeters( $tx*$this->tileSize, $ty*$this->tileSize, $zoom ); | |
| list($maxx, $maxy) = $this->PixelsToMeters( ($tx+1)*$this->tileSize, ($ty+1)*$this->tileSize, $zoom ); | |
| return array( $minx, $miny, $maxx, $maxy ); | |
| } | |
| /** | |
| * Resolution (meters/pixel) for given zoom level (measured at Equator) | |
| * @param $zoom | |
| * @return float | |
| */ | |
| function Resolution( $zoom ) { | |
| # return (2 * math.pi * 6378137) / (self.tileSize * 2**zoom) | |
| return $this->initialResolution / pow(2, $zoom); | |
| } | |
| /** | |
| * Returns bounds of the given tile in latutude/longitude using WGS84 datum | |
| * @param $tx | |
| * @param $ty | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function TileLatLonBounds($tx, $ty, $zoom ) { | |
| $bounds = $this->TileBounds( $tx, $ty, $zoom); | |
| list($minLat, $minLon) = $this->MetersToLatLon($bounds[0], $bounds[1]); | |
| list($maxLat, $maxLon) = $this->MetersToLatLon($bounds[2], $bounds[3]); | |
| return array( $minLat, $minLon, $maxLat, $maxLon ); | |
| } | |
| /** | |
| * Maximal scaledown zoom of the pyramid closest to the pixelSize. | |
| * @param $pixelSize | |
| * @return int | |
| */ | |
| function ZoomForPixelSize($pixelSize) { | |
| foreach (range(0, 30) as $i) { | |
| if ($pixelSize > $this->Resolution($i)) { | |
| return $i != 0 ? $i - 1 : 0; # We don't want to scale up | |
| } | |
| } | |
| } | |
| /** | |
| * Converts TMS tile coordinates to Google Tile coordinates | |
| * @param $tx | |
| * @param $ty | |
| * @param $zoom | |
| * @return array | |
| */ | |
| function GoogleTile($tx, $ty, $zoom) { | |
| # coordinate origin is moved from bottom-left to top-left corner of the extent | |
| return array($tx, (pow(2, $zoom) - 1) - $ty); | |
| } | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment