There are 2 ways to make search engines aware of a sitemap's location that I know of:
- Include an absolute link to it in
- Submit it to them directly. The relevant URLs are:
SITEMAP_URL is the absolute URL of the sitemap. Currently, I do both. Regarding (2), I have a job that runs automatically every day which submits the sitemap to Bing and Google. I don't think there's any reason to do (1) and (2), but I'm paranoid, so I do.
I imagine you can avoid both (1) and (2) if you just make your sitemap accessible at a conventional URL (like robots.txt). What's the simplest and most reliable way to ensure that search engines can find your sitemap?