var ge;
   
    // store the object loaded for the given file... initially none of the objects
    // are loaded, so initialize these to null
    var currentKmlObjects = {
      '1': null,
      '2': null,
      '3': null,
      '4': null,
      '5': null,
      '6': null
    };
   
    google.load("earth", "1");
   
    function init() {
      google.earth.createInstance('map3d', initCallback, failureCallback);
   
      addSampleUIHtml(
        '<h3>Legend</h3>' + 'Click to toggle<br/>' +
        '<input type="checkbox" id="pt_1_v2" onclick="toggleKml(\'1\');"/><label for="pt_1_v2">Part 1</label><br/>' +
        '<input type="checkbox" id="pt_2_v2" onclick="toggleKml(\'2\');"/><label for="pt_2_v2">Part 2</label><br/>' +
        '<input type="checkbox" id="pt_3_v2" onclick="toggleKml(\'3\');"/><label for="pt_3_v2">Part 3</label><br/>' +
        '<input type="checkbox" id="pt_4_v2" onclick="toggleKml(\'4\');"/><label for="pt_4_v2">Part 4</label><br/>' +
        '<input type="checkbox" id="pt_5_v2" onclick="toggleKml(\'5\');"/><label for="pt_5_v2">Part 5</label><br/>' +
        '<input type="checkbox" id="pt_6_v2" onclick="toggleKml(\'6\');"/><label for="pt_6_v2">Part 6</label><br/>'
      );
    }
   
    function initCallback(instance) {
      ge = instance;
      ge.getWindow().setVisibility(true);
   
      // add a navigation control
      ge.getNavigationControl().setVisibility(ge.VISIBILITY_AUTO);
   
      // add some layers
      ge.getLayerRoot().enableLayerById(ge.LAYER_BORDERS, true);
      ge.getLayerRoot().enableLayerById(ge.LAYER_ROADS, true);
   
      // fly to Santa Cruz
      var la = ge.createLookAt('');
      la.set(37, -122,
        0, // altitude
        ge.ALTITUDE_RELATIVE_TO_GROUND,
        0, // heading
        0, // straight-down tilt
        10000000 // range (inverse of zoom)
        );
      ge.getView().setAbstractView(la);
   
      // if the page loaded with checkboxes checked, load the appropriate
      // KML files
      if (document.getElementById('pt_1_v2').checked)
        loadKml('1');
   
      if (document.getElementById('pt_2_v2').checked)
        loadKml('2');
   
      if (document.getElementById('pt_3_v2').checked)
        loadKml('3');
     
      if (document.getElementById('pt_4_v2').checked)
        loadKml('4');
     
      if (document.getElementById('pt_5_v2').checked)
        loadKml('5');
     
      if (document.getElementById('pt_6_v2').checked)
        loadKml('6');
   
      document.getElementById('installed-plugin-version').innerHTML =
        ge.getPluginVersion().toString();
    }
   
    function failureCallback(errorCode) {
    }
   
    function toggleKml(file) {
      // remove the old KML object if it exists
      if (currentKmlObjects[file]) {
        ge.getFeatures().removeChild(currentKmlObjects[file]);
        currentKmlObject = null;
      }
   
      // if the checkbox is checked, fetch the KML and show it on Earth
      var kmlCheckbox = document.getElementById('pt_' + file + '_v2');
      if (kmlCheckbox.checked)
        loadKml(file);
    }
   
    function loadKml(file) {
      var kmlUrl = 'http://www.sladeride.com/msc-data/kml/pt_' + file + '_v2.kml';
   
      // fetch the KML
      google.earth.fetchKml(ge, kmlUrl, function(kmlObject) {
        // NOTE: we still have access to the 'file' variable (via JS closures)
   
        if (kmlObject) {
          // show it on Earth
          currentKmlObjects[file] = kmlObject;
          ge.getFeatures().appendChild(kmlObject);
        } else {
          // bad KML
          currentKmlObjects[file] = null;
   
          // wrap alerts in API callbacks and event handlers
          // in a setTimeout to prevent deadlock in some browsers
          setTimeout(function() {
            alert('Bad or null KML.');
          }, 0);
   
          // uncheck the box
          // document.getElementById('kml-' + file + '-check').checked = '';
        }
      });
    }

function addSampleButton(caption, clickHandler) {
        var btn = document.createElement('input');
        btn.type = 'button';
        btn.value = caption;
       
        if (btn.attachEvent)
          btn.attachEvent('onclick', clickHandler);
        else
          btn.addEventListener('click', clickHandler, false);

        // add the button to the Sample UI
        document.getElementById('sample-ui').appendChild(btn);
      }
     
function addSampleUIHtml(html) {
        document.getElementById('sample-ui').innerHTML += html;
}