The squares are 50cm. As you can see there is not much space, basically a truncated 6m x 8m plot. The right hand half is what I bought from my neighbour. The rest of my garden does extend below the piece you see here for about another 20m or so but contains among other things a small orchard (well, three fruit trees) a swimming puddle and a greenhouse. There is room for a branch line to meander through some of this at some point but you have to start small and think big. I see this as the large scale equivalent of a PIKO or LGB G scale starter set; an oval of track, loco, few trucks, only 3 times bigger.
I would have preferred 7 1/4" gauge but no way could I get a circuit in my garden. I did consider an "end-to-end" line which would have allowed larger curves but I have been persuaded by various arguments that a circuit is better especially for (grand)children whether riding or driving. So 5" gauge it is.
Where I'm at is that I have completed half the track bed, half built the new shed/tunnel, and I collected the track today. Most of the time since I started this madcap scheme in January has been clearing the new plot and moving my shed. To get the circuit shown in the plan above I had to move the shed about 1m right and 50cm down. That was a story in itself, and required me to pack up my indoor G scale layout - the primary use of the shed - and empty the contents into another shed, which is now morphing into the loco shed / tunnel at the top of the plan. The loco and driving truck are on order. The plan is to have the trackbed and shed complete in June, lay the track in July, ready for the arrival of the loco in August.
I'm going for a battery powered loco, not steam or petrol, mainly because of the dangers to grandchildren but also because it seems easiest to start with (like the starter set mentioned earlier).
I will post some pictures as I progress and ask many questions along the way. All I have done so far is standard gardening and DIY, I haven't started the garden rails stuff yet!

