/// <summary>
/// 更新地图显示
/// </summary>
private void UpdateMapImg()
{
Graphics g = Graphics.FromImage(mapImg);
g.Clear(Color.White);
myMap.DrawMap(g, picBoxMap.Bounds, centerLngLat, ratio * scaleChoice[scaleIndex]);
picBoxMap.Image = mapImg;
g.Dispose();
}
