This two-page article was published is in the March, 2002 issue of Model Railroader magazine.  In addition, a fun, interactive version of the photo is
on their website at "How to photograph a bird's-eye view of your layout." 

  
The article was submitted in November of 2000, so the composite photo is somewhat dated.   But you can see an updated version of the composite here on my website on my "Aerial Photo" page.  (Aren't you lucky?)