Well, now I have an accurate set of floor plans, I can compare the estimates that I worked out using Google Maps (see previous post).
I estimated the overall size of the buildings (including the barn) to be around 20 feet by 80 feet. The floor plans (and the topo survey) show that the building is in fact 22 feet by 82 feet. Remarkably close to the Google Map estimate. I tried a few other measurements that I had taken and they are all within about 10% of the actual measurement – this is particularly the case with longer measurements. It is pretty scary about how much detail you can glean from these satellite images.