Officially, How are grid squares counted?

I ran into a situation recently where an individual was counting Residential areas as being 4x4 and small parks and water towers as being 2x2.  His take is that he is counting from the center of the structure.

An example that was used was based on the Area of Influence of the Ferris wheel.  When I broke it down to prove the 20x20 coverage of the Ferris wheel, I found the Ferris Wheel's area of influence to actually be 21x21 and not 20x20 as it shows in the Entertainment screen as there is an extra .5 extra coverage on either side giving a 21 count total.

Based on his logic of going from the center of the structure and counting 1/2 the width of a road segment as 1, there is exactly a 20 count.

Supporting images for both are attached.

What I'm looking to answer is Officially, how is it counted?

Please keep in mind that this is not about one person being right or wrong, just informational so everyone is speaking the same language when talking about the game.

Thanks You.