I can get an esri base map to overlay on top of onemap but it does not work the other way round I think it may be a projection problem, try the following code in the javascript sandbox:http://developers.arcgis.com/javascript/sandbox/sandbox.html
<!DOCTYPE html>
<html>
<head>
<script type='text/JavaScript' src='http://www.onemap.sg/API/JS?accessKEY=xkg8VRu6Ol+gMH+SUamkRIEB7fKzhwMvfMo/2U8UJcFhdvR4yN1GutmUIA3A6r3LDhot215OVVkZvNRzjl28TNUZgYFSswOi'></script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no"/>
<title>Simple Map</title>
<link rel="stylesheet" href="http://js.arcgis.com/3.9/js/esri/css/esri.css">
<style>
html, body, #map {
height: 100%;
width: 100%;
margin: 0;
padding: 0;
}
body {
background-color: #FFF;
overflow: hidden;
font-family: "Trebuchet MS";
}
</style>
<script src="http://js.arcgis.com/3.9/"></script>
<script language="JavaScript" type="text/JavaScript">
var map;
var centerPoint="28968.103,33560.969";
var myLayer = new esri.layers.ArcGISDynamicMapServiceLayer("http://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer");
myLayer.opacity = 0.5;
var OneMap = new GetOneMap('map','SM',{level:7,center:centerPoint,layer:myLayer}); //add one map here
function init() {
map=OneMap.map;
dojo.connect(OneMap.map, "onExtentChange", showExtent);
}
dojo.addOnLoad(init);
</script>
</head>
<body>
<div id="map"></div>
</body>
</html>
RegardsAnthony
