Google Maps Tile-related operations (Js,google maps v3)

Some time ago, due to work reasons, the study of Google Maps tile-related operations. Know the latitude and longitude of a point and the map level, get the URL of the tile where the point resides; the URL of a tile is known, the upper-left corner of the tile is computed, the latitude and longitude of the tiles are known, and the pixel values on the world map are computed for a point latitude and longitude and map level.

1, know the latitude and longitude of a point and map level, get the URL of the tile where the point resides

Reference to two blog: this blog (http://blog.csdn.net/lijun_xiao2009/article/details/8178578) in the principle, but the use of the formula is too difficult to forget, combined with another blog (http:// BLOG.CSDN.NET/ZHAOBMOX/ARTICLE/DETAILS/1253005) inside the operation.

Manage Tile path function Calculationurl (val_lat,val_lng) {val_lng = parsefloat (VAL_LNG); Val_lat = parsefloat (Val_lat); var val_zoom = mapattr.cutzoom;//map level, set to global variable var zoomn = Math.pow (2,val_zoom); var x = Calc ULATIONLNG (VAL_LNG); var y = Calculationlat (Val_lat);//urldivvar url_x = X*zoomn;var url_y = Y*zoomn;return [Math.floor ( url_x), Math.floor (url_y)];} Calculate tile x-value function calculationlng (LNG) {var x = (180.0 + parsefloat (LNG))/360.0;return x according to longitude;}  Calculates the tile y-value function Calculationlat (LAT) {var PI = Math.pi;//3.1415926535897;var y =-parsefloat (lat) * pi/180; y = 0.5 * per latitude Math.log ((1+math.sin (Y))/(1-math.sin (y))); Y *= 1.0/(2 * PI); Y + = 0.5;return y;}

The resulting data is spelled ".../' +zoom+ '/' +x+ '/' +y+ '. png '", zoom is the map level and XY is the data just calculated.

2, the URL of a tile is known, calculate the top left corner of the tile latitude and longitude

Reference the blog: http://www.cnblogs.com/Tangf/archive/2012/04/07/2435545.html

function calculationlatlng (x, y) {var PI = Math.pi;var Zoomn = Math.pow (2,mapattr.cutzoom);//map level, set as global variable var LNG = X/zoomn *360.0-180.0;var a = pi* (1-2*y/zoomn), var e = Math.e;var rad = (Math.pow (e,a)-math.pow (e,-a)) *0.5var Latrad = Math.atan (ra D) var lat = latrad*180.0/pi;return {"lat": Lat, "LNG": LNG};}

3, known a point latitude and longitude and map level, calculate this point on the world map of the pixel value

Refer to the Baidu Library: http://wenku.baidu.com/link?url= Lg31km26tjhtytmbkwmq92lneu7p-aukeowfrej62rbsgrc7sive9vk2rq64sk0dlmvfs1zeidmx44sklxvzyct_njw2guhjqyxksxbvmak

Calculates the pixel value of a point on the world map function calculationpixeldistance (lat,lng) {var zoom = Mapattr.cutzoom;<span style= "font-family : Arial, Helvetica, Sans-serif; >//map level, set to global variable </span>//the coordinates of the first tile of the world map with the pixel var X = lngtopixel_x (lng,zoom); var Y = lattopixel_y (lat,zoom); return {X:math.floor (x), Y:math.floor (Y)};} Calculates x-pixel values by longitude function lngtopixel_x (lng,zoom) {return (lng+180) * (256<<zoom)/360;} Calculates y-pixel values according to Latitude function lattopixel_y (lat,zoom) {var siny = Math.sin (lat*math.pi/180); var y = Math.log ((1+siny)/(1-siny)) Return (128<<zoom) * (1-y/(2*MATH.PI));}

Google Maps Tile-related operations (Js,google maps v3)