これで、各ズームレベルの地図上の各位置を正確に示すことができるようになりました。Maps JavaScript API は、ズームレベル、地図の中心（LatLng）、および含まれる DOM 要素のサイズが指定されると、ビューポートを構成し、この境界ボックスをピクセル座標に変換します。次に、API は指定されたピクセル境界内に入るすべての地図タイルを論理的に決定します。これらの地図タイルはそれぞれタイル座標を使用して参照されます。これにより、地図画像の表示が非常に簡単になります。
タイル座標
ズームレベルが高い場合、API ですべての地図画像を一度に読み込むことはできません。代わりに API は、各ズームレベルの画像を、地図タイルのグループに分割します。このタイルは、アプリケーションが判別する順序で論理的に配置されます。地図を新しい位置にスクロールする、または新しいズームレベルにスクロールすると、API はピクセル座標を使用して必要なタイルを決定し、そのピクセル座標の値を取得するタイルのグループに変換します。これらのタイル座標は、指定されたポイントの画像を含むタイルを論理的に判別しやすくするスキームを使用して割り当てられます。
[[["わかりやすい","easyToUnderstand","thumb-up"],["問題の解決に役立った","solvedMyProblem","thumb-up"],["その他","otherUp","thumb-up"]],[["必要な情報がない","missingTheInformationINeed","thumb-down"],["複雑すぎる / 手順が多すぎる","tooComplicatedTooManySteps","thumb-down"],["最新ではない","outOfDate","thumb-down"],["翻訳に関する問題","translationIssue","thumb-down"],["サンプル / コードに問題がある","samplesCodeIssue","thumb-down"],["その他","otherDown","thumb-down"]],["最終更新日 2025-08-17 UTC。"],[[["\u003cp\u003eThe Maps JavaScript API uses four coordinate systems: latitude/longitude, world, pixel, and tile coordinates.\u003c/p\u003e\n"],["\u003cp\u003eWorld coordinates are derived from latitude/longitude using the Mercator projection and represent a point on the map.\u003c/p\u003e\n"],["\u003cp\u003ePixel coordinates specify a pixel on the map at a given zoom level and are calculated from world coordinates.\u003c/p\u003e\n"],["\u003cp\u003eTile coordinates identify a specific map tile at a particular zoom level, crucial for efficient map loading.\u003c/p\u003e\n"],["\u003cp\u003eEach zoom level quadruples the resolution and pixel space compared to the previous level due to the tiling system.\u003c/p\u003e\n"]]],[],null,["# Map and Tile Coordinates\n\nSelect platform: [Android](/maps/documentation/android-sdk/coordinates \"View this page for the Android platform docs.\") [iOS](/maps/documentation/ios-sdk/coordinates \"View this page for the iOS platform docs.\") [JavaScript](/maps/documentation/javascript/coordinates \"View this page for the JavaScript platform docs.\")\n\nThe Maps JavaScript API uses the following coordinate systems:\n\n- Latitude and longitude values, which reference a point on the world uniquely. (Google uses the [World Geodetic\n System WGS84](https://en.wikipedia.org/wiki/World_Geodetic_System) standard.)\n- World coordinates, which reference a point on the map uniquely.\n- Pixel coordinates, which reference a specific pixel on the map at a specific zoom level.\n- Tile coordinates, which reference a specific tile on the map at a specific zoom level.\n\nWorld coordinates\n-----------------\n\nWhenever the API needs to translate a location in the world to a location on\na map, it first translates latitude and longitude values into a\n*world* coordinate. The API uses the\n[Mercator\nprojection](https://en.wikipedia.org/wiki/Mercator_projection) to perform this translation.\n\nFor convenience in the calculation of pixel coordinates (see below)\nwe assume a map at zoom level 0 is a single tile of the base tile size.\nWe then define world coordinates relative to pixel coordinates at zoom\nlevel 0, using the projection to convert latitudes and longitudes to\npixel positions on this base tile. This world coordinate is a floating\npoint value measured from the origin of the map projection to the\nspecific location. Note that since this value is a floating point value,\nit may be much more precise than the current resolution of the map image\nbeing shown. A world coordinate is independent of the current zoom level,\nin other words.\n\nWorld coordinates in Google Maps are measured from the Mercator\nprojection's origin (the northwest corner of the map at 180 degrees\nlongitude and approximately 85 degrees latitude) and increase in\nthe `x` direction towards the east (right) and increase in\nthe `y` direction towards the south (down). Because the\nbasic Mercator Google Maps tile is 256 x 256 pixels, the usable\nworld coordinate space is `{0-256}, {0-256}`.\n\nNote that a Mercator projection has a finite\nwidth longitudinally but an infinite height latitudinally. We cut off\nbase map imagery utilizing the Mercator projection at approximately\n+/- 85 degrees to make the resulting map shape square, which allows\neasier logic for tile selection. Note that a projection may produce\nworld coordinates outside the base map's usable coordinate space\nif you plot very near the poles, for example.\n\nPixel coordinates\n-----------------\n\n*Pixel coordinates* reference a specific pixel on the map at a\nspecific zoom level, whereas world coordinates reflect absolute locations on a\ngiven projection. Pixel coordinates are calculated using the following\nformula: \n\n```javascript\npixelCoordinate = worldCoordinate * 2zoomLevel\n```\n\nFrom the above equation, note that each increasing zoom level\nis twice as large in both the `x` and `y`\ndirections. Therefore, each higher zoom level results in a resolution four\ntimes higher than the preceding level. For example, at zoom level 1,\nthe map consists of 4 256x256 pixels tiles, resulting in a pixel space\nfrom 512x512. At zoom level 19, each `x` and `y` pixel\non the map can be referenced using a value between\n0 and 256 \\* 2^19^.\n\nBecause we based world coordinates on the map's tile size, a\npixel coordinate's integer part has the effect of identifying the exact pixel\nat that location in the current zoom level. Note that for zoom level 0, the\npixel coordinates are equal to the world coordinates.\n\nWe now have a way to accurately denote each location on the map,\nat each zoom level. The Maps JavaScript API constructs a viewport\ngiven the zoom level center of the map (as a `LatLng`) and the\nsize of the containing DOM element, and\ntranslates this bounding box into pixel coordinates. The API then determines\nlogically all map tiles which lie within the given pixel bounds. Each of\nthese map tiles are referenced using [tile coordinates](#tile-coordinates) which greatly simplify the displaying of map\nimagery.\n\nTile coordinates\n----------------\n\nThe API cannot load all the map imagery at once for the higher zoom levels.\nInstead, the API breaks up the imagery at each zoom level\ninto a set of map tiles, which are logically arranged in an order which the\napplication understands. When a map scrolls to a new location, or to a new\nzoom level, the API determines which tiles are needed\nusing pixel coordinates, and translates those values into a set\nof tiles to retrieve. These tile coordinates are assigned using\na scheme which makes it logically easy to determine which tile contains\nthe imagery for any given point.\n\nTiles in Google Maps are numbered from the same origin as that\nfor pixels. For Google's implementation of the Mercator projection, the\norigin tile is always at the northwest corner\nof the map, with `x` values increasing from west to\neast and `y` values increasing from north to south. Tiles\nare indexed using `x,y` coordinates from that origin. For\nexample, at zoom level 2, when the earth is divided up into 16 tiles,\neach tile can be referenced by a unique `x,y` pair:\n\nNote that by dividing the pixel coordinates by the tile size (256) and\ntaking the integer parts of the result, you produce as a by-product\nthe tile coordinate at the current zoom level.\n\nExample\n-------\n\nThe following example displays coordinates for Chicago, IL:\nlatitude/longitude values, world coordinates, pixel coordinates, and tile\ncoordinates. Use the zoom control to see the coordinate values at various\nzoom levels.\n\nTo see how the coordinates were calculated,\n[view\nthe code](/maps/documentation/javascript/examples/map-coordinates)."]]
