Reconstruction of the
2000 North Down formation
1. Draw a circle. It forms the outer border of the formation.
2. Construct a regular 11-fold polygon inscribed in this circle. (Note that this can not be done by the strict "ruler-and-compass" construction method; the corner-points can be found by calculating the coordinates).
3. Construct the inscribed circle of the polygon. It forms the inner border of the ring.
4. Draw all the diagonals of the polygon from corner-points four apart.
5. Construct the inscribed circle of the diagonals. It forms the inner circle of the formation.
6. Draw the 11 "rays" from the center to the corner-points of the polygon.
7. Construct a circle, centered at the intersection of the inner ring border and a ray, and tangent to the inner circle, as shown.
8. Repeat this for all 11 rays.
9. Construct a circle, centered at the intersection of the inner circle and a ray, and tangent to two circles of step 8, six apart, three to the left and three to the right, as shown.
10. Construct a circle, concentric with the one of step 7, and tangent to the last circle (step 9) at the far side, as shown.
11. Copy a circle of step 9 with its center at the righthand side intersection of the large circle of step 10 and the inner ring border, as shown.
12. Repeat this for all 11 directions. Now, all necessary parts are ready.
13. Trimming away all superfluous parts will yield the reconstruction of the 2000 North Down formation.
14. The final result, matched with the aerial image.
Copyright © 2000, Zef Damen, The Netherlands

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