CKey locator format v0.12.0 (draft)

Status: experimental reference format. Encoder output uses format=12 (0C) and profile=1. Formats 8 and 11 remain accepted by the reference decoder for historical fixtures, but are not emitted.

Canonical geometry

The field is 29 by 29 units, origin upper-left, with centre (14.5,14.5). The outer structure is a rounded square from (0.5,0.5) to (28.5,28.5), radius 3.5, width 0.65. It is monochrome; colour is decorative only.

Each finder is one broad rounded-corner arc integrated with the structural corner, rather than multiple nested arcs or an inward-protruding leaf. In local top-left coordinates the arc centre is (3.20,3.20), its centreline radius is 2.30, and width is 0.80, with round caps. Top-right, bottom-right, and bottom-left are exact reflections and have continuous arcs. The top-left arc is split at the 45-degree diagonal. Cap compensation produces a 0.95-unit clear visible gap. That gap is the finder orientation signature. All four 6 by 6 corner envelopes are non-payload.

The polar geometry is unchanged from v0.8.0: four rings at radii 3.6 + .8r with 72 five-degree slots, a separate dial band at radii 7.6--9.5, and a logo-safe centre inside radius 3.3. The Grid Key is the 2 by 2 block at rows 11--12/columns 2--3. The Ray Key is 12:00/full, 9:00/half, and 9:05/ three-quarter. The Ring Key is dots at slots 18,19,21, an explicit empty slot 20, then a connected round-capped four-slot arc at 22--25. Dot and arc width are 0.30; the arc visible length equals four dot slots exactly.

Frame, ECC, and placement

The locator carries exactly 16 bytes. The systematic frame is C7 4B 0C 01 00 10, payload, then CRC-32C of the first 22 bytes. It is encoded as shortened systematic RS(77,26) over GF(256), primitive polynomial 0x11D, primitive element 2, roots alpha^0...alpha^50, high-degree first, with 51 parity bytes. The algebraic bound is 25 unknown byte errors.

The 616 bits are mapped MSB-first by the established alternating Cartesian/polar placement: angularly interleaved Cartesian cells, all 69 data dial rays, then round-robin inner ring sites. Structural border, finder envelopes, Grid/Ray/Ring Keys, and the polar aperture are reserved. The reader rectifies a supplied quadrilateral and uses permanent keys plus the rounded finder signature as geometric evidence; it accepts payloads only after RS and CRC validation. Finder shape is never a substitute for that mathematical validation.

The normative byte vector is locator-v12.json.