private void RefreshScaleText(Size actualSize)
{
var viewRect = new Rect(new Point(), actualSize);
var centerPoint = new Point(viewRect.Width / 2.0, viewRect.Height / 2.0);
var scale = Scale * Math.Min(centerPoint.X, centerPoint.Y);
var textBrush = (Brush)FindResource("SystemMapScaleTextBrush");
var scaleWidth = (double)FindResource("SystemMapScaleWidth");
m_scaleText = new FormattedText(FormatUtility.RenderDistance(scaleWidth / scale), CultureInfo.CurrentUICulture, FlowDirection.LeftToRight, new Typeface("Verdana"), 12, textBrush, 1.0);
}