// event handler for tile changes
 public void OnReceieveOsmTile(object sender, LonLatStringEventArgs e)
 {
     this.Latitude = e.Latitude;
                 this.Longitude = e.Longitude;
 }
 // event handler for lat/lon changes
 public void OnReceiveLonLat(object sender, LonLatStringEventArgs e)
 {
     this.XColumn = OsmTile.XColFromLon(e.Longitude, _tile.Zoom);
                 this.YRow = OsmTile.YRowFromLat(e.Latitude, _tile.Zoom);
 }