Display error using google maps tile server and Google Maps utility in PHP -

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i have question regarding map tile server , coordinates conversion in google maps using google maps utility library.

my tile server accesses database thousands of gps coordinates (lat,lng), , every (lat,lng) point, checks if point inside geographical bounds of tile; if does, coordinates conversion (wgs84 -> mercator -> x,y offset inside tile) , paints corresponding pixel inside tile, using googlemapsutility library.

in terms of code, following:

$point = googlemaputility::getoffsetpixelcoords((float)$row['lat'], (float)$row['lng'], $zoom, $x, $y);

which calls getoffsetpixelcoords function (and in turn functions below) library:

public static function getoffsetpixelcoords($lat,$lng,$zoom, $x, $y)      {         $pixelcoords = googlemaputility::getpixelcoords($lat, $lng, $zoom);         return new point(             $pixelcoords->x - $x * googlemaputility::tile_size,              $pixelcoords->y - $y * googlemaputility::tile_size         );     }   public static function getpixelcoords($lat, $lng, $zoom)      {         $normalised = googlemaputility::_tonormalisedmercatorcoords(googlemaputility::_tomercatorcoords($lat, $lng));         $scale = (1 << ($zoom)) * googlemaputility::tile_size;         return new point(             (int)($normalised->x * $scale),              (int)($normalised->y * $scale)         );     }  private static function _tonormalisedmercatorcoords($point)      {         $point->x += 0.5;         $point->y = abs($point->y-0.5);         return $point;     }

ok, results. zoom level<13 works great, below example of tile in zoom level 11:

image1

however, tile in zoom level >13, following happens:

image2

which strange... pixels seem aligned ? @ first thought decimal resolution problem, resolution of data quite (stored double in mysql database, example, 35.6185989379883, 139.731994628906, , in php floats , doubles same thing...)

could me on how fix problem?

thanks in advance...

why use type casting on result of database query? in example of book googlemapsutility it's not there?


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