Recently I wanted to know how big a certain no longer in use real life turntable and engine shed were, as I wanted to have the correct size on my layout. Also the size of some silos and buildings on a particular grain elevator that I wanted to scratch build were proving a challenge as port security frowns on people walking around restricted areas with cameras and measuring tapes. My solution was google earth. I just zoomed in on what I wanted to measure, set the measuring tool to feet and instant accurate success. One could also use this to measure railyards, piers or like I did a certain rail barge I want to also build.
Great idea , I certainly never thought of measuring with Google Earth. I use it all the time. Great shots of some of the great yards around the country.