refreshImage() {
    var name = 'lights';
    var params = $.param(this.getYearParam());
    var path = '/mapid?' + params;
    if (this.layerPaths[name] == path) {
      return;  // If the map hasn't changed since the last update, exit early.
    } else {
      this.removeLayer(name);
      // Encode the parameters in the URL.
      this.setLayer(name, path, false);
    }
  }
Updates the image based on the current control panel config.