I am doing some market research, and aim to create several landing pages aimed at long tail searches.Do these landing pages need to be in the navigation, or have an incoming link from somewhere else on the website, in order to be included in Google's index?I don't want to include them in the navigation, because some of the landing pages will be addressing similar search terms, and they will look silly being listed next to each other if they are so similar.Likewise, I don't want to necessarily use a Sitemap page, which links to the landing pages.  I don't want a website visitor know I use a variety of landing pages to entice traffic.So, is it possible for isolated, stand alone webpages to be included in the Google index?
Can I have stand alone webpages indexed by Google?
google index
The idea of landing pages is to be isolated from your website. Therefore, you shouldn't put links to them from your website.Moreover, you don't necessarily need a sitemap.xml or a link from your website to tell Google to index your webpages. You just need backlinks to these landing pages and the best approach in your case is to obtain these links from external websites.That way, Googlebot will follow these links and will find your landing pages to put them into its index.Thus the answer to your question is yes.