code: function(terria, url) {
    CatalogItem.call(this, terria);
  
    this._geoJsonItem = undefined;
  
    this.url = url;
  
    /**
     * Gets or sets the Gpx data, represented as a binary Blob, DOM Document, or a Promise for one of those things.
     * If this property is set, {@link CatalogItem#url} is ignored.
     * This property is observable.
     * @type {Blob|Document|Promise}
     */
    this.data = undefined;
  
    /**
     * Gets or sets the URL from which the {@link GpxCatalogItem#data} was obtained.  This may be used
     * to resolve any resources linked in the Gpx file, if any.
     * @type {String}
     */
    this.dataSourceUrl = undefined;
  
    knockout.track(this, ["data", "dataSourceUrl"]);
  }
docs: A {@link CatalogItem} representing GPX data.
  
  @alias GpxCatalogItem
  @constructor
  @extends GeoJsonCatalogItem
  
  @param {Terria} terria The Terria instance.
  @param {String} [url] The URL from which to retrieve the GPX data.