О немО себе[code]/maps/Мои СоседиМой ЗимаШопМоя СтройкаЗверь Дверь

Mission:Make loading a bit faster, and a bit cleaner

Goal:Load data in set of information tiles

Step 1. Load data into map

Lets request server for tiles in visible viewport

$.get("ajax/load-map-data?SE="+MySECorner.toString()+"&NE="+MyNECorner.toString()+"&zoom"+currentZoom,
      function(data){
        //wow! i got the data for map!
        //forwhole visible viewport( and just for it)
      });

Step 2. Kill users, server and youself

Just answer two single things
  • will you rerequest data if maps is moved by pixel
  • can you cache request
If first answer is "no" and sencond is "no" - close this page. You allready find nirvana :)
And if you still here - you load your data in wrong way, yet. Until now.

Step 3. How google loads image for tiles?

He(it?) loads it in.. tiles :)

Step 4. Think! Why not to do same?

If you load you marker data in set of tiles -
  • you can Perfectly cache them
  • Map shift below 256px will not preduce any requests to server
  • Normal browser can perform 4-6 request to one server at one moment, so you`ll ask tiles in parrallel, 4-6 times faster
Define your own tile source, not for image tiles, but for data tiles


var ServerFetchedTiles=[];

function ServerFetchMapType() {
}

ServerFetchMapType.prototype.tileSize = new google.maps.Size(256,256);
ServerFetchMapType.prototype.maxZoom = 32;
ServerFetchMapType.prototype.name = "Server Tile #s";
ServerFetchMapType.prototype.alt  = "Server Data Tile Map Type";      

ServerFetchMapType.prototype.getTile = function(coord, zoom, ownerDocument) {
  var addr=this.getAddr(coord,zoom);
  //test - may be we allready load this block?
  if(ServerFetchedTiles[addr]){
    return
  }
  $.get("ajax/load-map-tile?"+addr,
      function(data){
        ServerFetchedTiles[addr]=data;
        //wow! i got the data just for this tile
        //and any map moving is nothing for me!
      });
};

//and add this tile overlay to current map type
map.overlayMapTypes.insertAt(0, new ServerFetchMapType() );

And you can request tiles by two ways - as google do (x,y,z), or as latlngbox. I write some code for second variant( i think you`ll use second at the begining)

//we can request tile as tile(x,y,z)
ServerFetchMapType.prototype.getAddrXY = function(coord, zoom){
   return "x="+coord.x+"&y="+coor.y+"&z="+zoom;
}

//or as latlng box
ServerFetchMapType.prototype.getAddrLatLng = function(coord, zoom){
    
    //helper function for mercator projection
   var mercator = function(point){
     //
     var numtiles=Math.pow(2,point.zoom);
     var bitmapsize=numtiles*256;
     var bitmaporigo       =bitmapsize/2;
     var pixelsperlondegree=bitmapsize/360;
     var pixelsperlonradian=bitmapsize/(2*Math.PI);
     
     var lat=bitmaporigo+(pixelsperlondegree*point.x);
     var ged2rad=((point.t*Math.PI)/180.0);
     var sn=Math.sin(deg2rad);
     var lng=((bitmaporigo - 0.5 * log((1+sn)/(1-sn)) * pixelsperlonradian));
     return new google.maps.LatLng(lat,lng);
   }
   var point1={x:coord.x*256,y:coord.y*256,z:zoom} ;
   var point2={x:(coord.x+1)*256,y:(coord.y+1)*256,z:zoom} ;
   var ne=mercator(point1);
   var sw=mercator(point2);
   return "NE="+ne.toString()+"&SW="+sw.toString()+"&z="+zoom;
}
more info about map tiles can be found at google code, and there they point this idea somehow. Idea - you can load not only images

Step 5. Enjoy

Now try to impliment pieces of this into your own code. Or see how it works on

What lasts?

Ask one questing - what you will do is there is no data for tile( you are viewing siberia ), may be just load tile for other zoom( currrent_zoom-2? ). And how we do it.

Homework: and why cites, listed above use other technics? Benefits of quadtree? ( ps: in this mode tiles can he cached on file level. For dirrect nginx access )


All of sections, i list here, is allready done by me. I need just to wrap code into article, and, yap, english article :)
If you want to know more - ask

Load data into google maps. And do it as google do

Все, хватит шутки шутить! Убивать тебя буду! Сообразив, что Кащей Бессмертный рассердился не на шутку, Иван распахнул какую-то дверь и юркнув в нее, сбежал по ведущей вниз лесенке.