gmap使用“层”

GMapOverlay routes = new GMapOverlay("routes");

 GMapOverlay polygons = new GMapOverlay("polygons");

  GMapOverlay markers = new GMapOverlay("markers"); 

gMapControl1.Overlays.Add(markers);

 gMapControl1.Overlays.Add(routes);

 gMapControl1.Overlays.Add(polygons);