The things being diagrammed
look to be specific items (in the center), as well as all the items surrounding them. In addition, since the answer is 13 letters, the blue dots probably aren't replacing letters in the answer, but should be considered on their own.
This leads to the aha moment -- that this chart
represents countries by their borders! The icons surrounding the center are rotated roughly to match the locations of the bordering nations; blue circles represent oceans.
For example, the top-right symbol represents Honduras - it has Guatemala and El Salvador bordering it to the northwest, Nicaragua to the southeast, and it also borders both the Pacific and Atlantic oceans.
The full answer:
As suggested, we "write out our findings in capitals" -- look at the capitals of the countries represented. These spell out the name for this diagram: CARTOGRAPHICS!