var map = new OpenLayers.Map("map", {

  projection: new OpenLayers.Projection("EPSG:900913"),

  displayProjection: new OpenLayers.Projection("EPSG:4326")

});

map.addControl(new OpenLayers.Control.Permalink());

map.addControl(new OpenLayers.Control.MousePosition());

var options = {

    projection: new OpenLayers.Projection("EPSG:900913"),//墨卡托投影

    units: "m",　　//以米为单位

    maxResolution: 156543.0339, //最大分辨率，0级 图上一个像素表示实际距离15万米多

    maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34,20037508.34, 20037508.34)

    //将地球分为4个卦象，156543.0339*128=20037508.34（为什么是*128，一个256*256的jpg中分，-128~128）

};

map = new OpenLayers.Map('map', options);

 var proj = new OpenLayers.Projection("EPSG:4326");

 var point = new OpenLayers.LonLat(119,40);

 point.transform(proj, map.getProjectionObject());


 map.setCenter(point);//地理坐标 

 var bounds = new OpenLayers.Bounds(-74.047185, 40.679648, -73.907005, 40.882078);

 bounds.transform(proj, map.getProjectionObject());