GMaps.js — Map Types

You can define many map types from external map services, like OpenStreetMap:

map.addMapType("osm", {
  getTileUrl: function(coord, zoom) {
    return "http://tile.openstreetmap.org/" + zoom + "/" + coord.x + "/" + coord.y + ".png";
  },
  tileSize: new google.maps.Size(256, 256),
  name: "OpenStreetMap",
  maxZoom: 18
});

You must define a function called getTileUrl, which returns a tile URL according the coordenates in the map.