Is my way for writing jquery plugin correct?

See more:

jQuery

I've started writing jquery plugin and I want:

To initialize it when I call it like this $('selector').sitemap(options);
To be able using some members(like 'loader', 'viewPort') in functions in plugin

Regard 1st: have I done it correctly in the way I wrote initialization(init function) or there is more correct\elegant way to do it?

Regard 2nd: in order to use members like 'loader', 'viewPort' I wrote all functions in sitemap object. have I done it right or there is more correct\elegant way to do it?

I'll be glad if you could suggest me Thank you very much

(function ($) {
    $.extend($.fn, {
        sitemap: function (options) {
            //check if applied on valid DIV element
            var canvas = this;
            if (!canvas.is('div')) return;
            var viewPort = null;
            var loader = $('<p id="initLoader">Loading...</p>');
            init();
            loadMap();
            function init() {
                //create viewPort div
                setCanvas();
            }
            function setCanvas() {
                         //set height and width
            }
            function loadMap() {
                viewPort.prepend(loader);
                buildMap($.parseJSON('{"pages":[]}'));
            }
            function buildMap(map){
              //...
           }
})(jQuery);

Thank you