The diagram depicts some points with latitude/longitude coordinates, along with one or more numbers. Searching up each of the coordinates leads to a windmill, and indexing the names of the windmills with the numbers gets you one or more letters associated with the point. Here's what this looks like (ordering here is by increasing x-coordinate):
- 51.955°N 6.271389°E (6)
- AURORA → A
- 52.960278°N 5.731944°E (15)
- DER SWEACHMERMOLEN → E
- 51.47817°N 0.17333°W (1)
- FOWLER'S MILL → F
- 51.053611°N 0.621389°E (1)
- ROLVENDEN → R
- 51.8317°N 0.6299°W (6,2)
- PITSTONE → O, I
- 50.824432°N 5.729508°E (6, 1, 18, 2, 26)
- TORENMOLEN VAN GRONSVELD, MAASTRICHT → M, T, S, O, S
- 53.266389 °N 5.930278°E (3)
- DE HOOP → H
- 37.764°N 122.508°W (4)
- MURPHY → P
- 51.901111°N 0.193889°E (4,1)
- STANSTED (MOUNTFITCHET) → N, S
- 41.654722°N 70.196667°W (9)
- JUDAH BAKER → E
- 51.242222°N 1.249444°E (1)
- CHILLENDEN → C
Now, you have a bunch of points with some letters on them. The assortment of points along with the flavortext clues Problem 2 from the 2011 International Mathematical Olympiad (IMO), which is about windmills!
For the extraction, you run the solution construction for the IMO problem using the points you have. The idea for solving the original windmill problem is to pick a line through a point such that there are an equal number of points on each side of the line. The flavortext clues “start[ing] by looking at the horizon,” meaning you should pick a horizontal line. For the line to have an equal number of points on each side, it must pass through the point with Cartesian coordinates (49,5) (corresponding to the letters N, S).
From here, run the windmill process (as described in the IMO problem), keeping track of the letters when you hit the corresponding point, and ending when the line returns to its original position (i.e. turns 180 degrees). Some points will be hit multiple times during the process, which is why some of them have multiple letters.
This gives: NAME OF THIS PROCESS, and the name of this process is WINDMILL.