online maps unity3d zoom problems

Hi,
when using unity3d with online maps, i can add an entity to the map to a certain point, but when i zoom-out or zoom-in the location of the object is changed, and just moving to anouther palce on the map.
when returning to the initial zoom level, the object returns to place.

should i be doing anything special?

my code:

    OnlineMaps api = OnlineMaps.instance;
    public Vector3 HPosition()
    {
        float Lat = model.Lat;
        float Lng = model.Lng;
        float Rad = model.Radius ;
        Vector3 position = OnlineMapsTileSetControl.instance.GetWorldPosition(Lng, Lat);
        position.y = -0.70f;
        return position;
    }
    public Quaternion HRotation()
    {
        float heading = 90;
        return Quaternion.Euler(0, heading, 0);
    }
    private void Update()
    {
       
        this.transform.rotation = HRotation();
        this.transform.position = HPosition();
        float k =Mathf.Pow(2,9);
        float scale = Mathf.Pow(2, api.zoom)/k;
        this.transform.localScale = scale * Vector3.one * model.Radius/15f;
    }