FA-70370 / GIS polygon topology / Member archive

Ring vertex cleaning with snapping tolerance: tolerance inclusivity · case 05

Vertices exactly one tolerance away from the previous vertex survive cleaning.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input [ring, eps] where ring is an open or closed list of integer [x, y] positions and eps >= 0. Walk the ring and drop a position whose Chebyshev distance to the last KEPT position is <= eps. Then repeatedly drop trailing kept positions within eps of the first kept position. If fewer than 3 positions remain return None, else return the kept positions closed by repeating the first.

Why this case matters

Digitised boundaries carry jitter and duplicate clicks; cleaning must not let small steps accumulate into dropped corners or leave near-closing duplicates.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
control #9	`[[23, 71], [30, 60], [32, 61], [24, 33], [25, 33], [28, 33], [26, 37], [23, 71]]`	`[[23, 71], [30, 60], [32, 61], [24, 33], [28, 33], [26, 37], [23, 71]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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