Hi Paul,
This is something I've been planning for 30 years...been visiting the Pomona Fair grounds Garden Railroad every year as long as I can remember (my inspiration). I had an indoor HO layout for many years, so I'm no stranger to model trains. And puttering in the garden is something my wife and I dearly love to do.
The area is about 85 feet long/across our back yard. It ranges in width/depth from 35 feet on each end of the yard to about 8 feet down the middle section.
I have a good preliminary track plan, and I'll finalize the exact route once I place/identify all the natural elements on the layout (boulders, rocks, canyons, trees, water features, etc - which is underway now).
I think of this project as a major landscaping project that happens to have a Railroad running through it.
Once I finish the first track loop (early next year) I'll start a thread discussing the various stages of construction....along with a short video.