function OverviewControl() {}
OverviewControl.prototype = new GControl();
OverviewControl.prototype.initialize = function(map) {
  var container = document.createElement("div");

  var back_to_overview_image = document.createElement("img");
  this.setButtonStyle_(back_to_overview_image);
  
  container.appendChild(back_to_overview_image);
  back_to_overview_image.src = 'img/maps/overview_icon.png';
  back_to_overview_image.title = 'zurück zur Übersichtskarte';
  GEvent.addDomListener(back_to_overview_image, "click", function() {
    show_kreis();
  });

  map.getContainer().appendChild(container);
  return container;
}
OverviewControl.prototype.getDefaultPosition = function() {
  return new GControlPosition(G_ANCHOR_BOTTOM_RIGHT, new GSize(7, 20));
}
OverviewControl.prototype.setButtonStyle_ = function(button) {
  button.style.textDecoration = "underline";
  button.style.color = "#0000cc";
  button.style.backgroundColor = "white";
  button.style.font = "small Arial";
  button.style.border = "1px solid black";
  button.style.padding = "2px";
  button.style.marginBottom = "3px";
  button.style.textAlign = "center";
  button.style.width = "6em";
  button.style.cursor = "pointer";
}