Google Earth is an amazing programme, especially its measurement tools. I have compared measuring buildings on Google Earth with an on the ground measurement and the difference is usually less than one metre. In fact using Google Earth can be as good as pacing the building out by foot and a whole lot quicker. It has a number of drawbacks of course, but it is ideal for a quick check of the foot print of a building.
There is a website that uses Google Earth to allow you to easily compare the relative sizes of building footprints and much more. It is called Mapfrappe, click here for link.
Its very simple to use. It uses two windows with maps, the top one is called the reference map. It is here that you find and draw a line around the base object you wish to use as a comparison.
You simple locate the object you wish to compare, using the search function if necessary. Then you draw a line around the perimeter of the object. Once done, you will see the same outline portrayed in the second window below. This lower window is called the reference map. You may need to zoom in if it is something small like a building outline. You can move around the globe to compare the outlined object against any other. I had a bit of fun with it:
First I outlined the building foot print of a large iconic building, The Pentagon building in Washington DC in this case. See below and note the blue lines around the building outer edge and inner courtyard.
Then in the comparison map I compared the foot print of The Pentagon with other large buildings. Here it is compared to Waterloo Train Station in London, click to enlarge.
And here it is compared to the New Century Global Centre in China, click to enlarge.
And to change things around slightly, here is the outline of the largest building in the World (by footprint) overlaid on the The Pentagon. Again click to enlarge.
You can compare different objects for ever, another one I did was the outline of Dublin (in blue) over-laid onLondon:
Of course it goes without saying that bigger isn’t better, but still this is a very clever website for comparing parts and objects in the World. There are lots of other interesting uses for instance: comparing Countries, lakes, counties, or even the route of your run overlaid on Rome or other historic city.