Regarding this blog post, its very easy to do visually. But for easy deployment on other environments I would like to do this in a powershell script.
I have found this information here: http://www.dotnetmafia.com/blogs/dotnettipoftheday/archive/2010/05/26/creating-enterprise-search-metadata-property-mappings-with-powershell.aspx
But its very unclear how to do it?