var map; 
var lat = "52.16";
var lon = "4.98";
var zoom = "10";

Proj4js.defs["EPSG:28992"] = "+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +towgs84=565.2369,50.0087,465.658,-0.406857330322398,0.350732676542563,-1.8703473836068,4.0812 +no_defs <>";
//Proj4js.defs["EPSG:28992"] = "+proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000  +ellps=bessel +towgs84=565.040,49.910,465.840,-0.40939,0.35971,-1.86849,4.0772";
Proj4js.defs["EPSG:900913"] = "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs";


function myFormat(lonLat) {
  var digits = parseInt(this.numdigits, 10);
  var newHtml =
    "Longitude: " +
    lonLat.lon.toFixed(digits) +
    " Latitude: " +
    lonLat.lat.toFixed(digits) +
    " (WGS84)";
  return newHtml;
}

function get_osm_url (bounds) {
  var res = this.map.getResolution();
  var x = Math.round ((bounds.left - this.maxExtent.left) / (res * this.tileSize.w));
  var y = Math.round ((this.maxExtent.top - bounds.top) / (res * this.tileSize.h));
  var z = this.map.getZoom();
  var path = z + "/" + x + "/" + y + "." + this.type;
  var url = this.url;
  if (url instanceof Array) {
    url = this.selectUrl(path, url);
  }
  return url + path;
}

function init() {
  map = new OpenLayers.Map ("map", {
	  controls:[
		  new OpenLayers.Control.Navigation(),
		  new OpenLayers.Control.MousePosition({formatOutput: myFormat, numdigits:3, div: $('coords')}),
        new OpenLayers.Control.MousePosition({
			  prefix: "RD Co&ouml;rdinaten (",
			  separator: ",",
			  suffix: ")",
			  displayProjection: new OpenLayers.Projection("EPSG:28992"),
			  numdigits: 0,
			  div: $('coordsRD')
		  })
	  ],
	  maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34),
	  maxResolution: 156543.0399,
	  numZoomLevels: 19,
	  units: 'm',
	  projection: new OpenLayers.Projection("EPSG:900913"),
	  displayProjection: new OpenLayers.Projection("EPSG:4326")
  });
  layerTileNL = new OpenLayers.Layer.TMS(
    "Mapnik",
    ["http://tile.openstreetmap.nl/tiles/"],
    {
      type:'png',
      getURL:get_osm_url
    }
  ); 
  map.addLayer(layerTileNL);
  if( ! map.getCenter() ){
    zoom = parseInt(zoom, 10);
    var lonLat = new OpenLayers.LonLat(lon, lat).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());
    map.setCenter (lonLat, zoom);
  }
}