Looks like we need a post here. Maybe this will help some of the new folks.
The San Juan Southern RR construction began with a 3-D scale model of the layout. Actually it began with a track plan designed with the free Atlas Right Track software. The the track plan was printed in 1" = 1' scale and glued to card stock and the model was built, ala Dave Frary in his very useful book on MRR scenery.