Pretty simple process to do from scratch. I'm in the middle of a fire rebuild design right now. I went to the site with my tablet and sketched the foundation, basement windows, as much of the underground plumbing as we could see, bearing walls, etc. (The fire started in the basement but most of the walls were still standing...the entire roof was pretty much gone) Part of the foundation will need to be removed per structural engineer. I've designed a completely different looking home using their existing foundation, adding a small section of new foundation, and a handful of cantilevers.
I should say that its much easier to measure once the builder had the balance of the home torn down and cleaned up. I measured with him right after the fire so we could get a contract in place with the owner and insurance company. Went back to double check things after everything was gone and had nearly everything right on...just a couple of walls that needed adjusting.