How does the tool handle GC-code base-31 and hexadecimal eras?

Codes up to GCFFFF are decoded as standard hexadecimal IDs (0 to 65535), while codes starting from GCG000 use the 31-character geocaching alphabet with a +411120 offset.

What happens if I type confusing characters like S or O into the GC-code field?

The validator automatically normalizes ambiguous characters like S to 5 and O to 0 to match canonical GC-code standards.

How are multiple projection legs calculated?

Legs are chained sequentially using forward great-circle equations on a 6,371,008.8-meter spherical model, feeding the result of each step into the next.

In what coordinate formats are the calculated waypoints displayed?

Results are output in standard WGS84 decimal degrees alongside the traditional DD° MM.mmm′ geocaching listing format.

Does this validator connect to live listing services?

No, it functions entirely as an offline mathematical and structural validator without making external network queries.

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Geocache Letterbox Munzee Stage-Cache Puzzle-Hunt Coordinate Validator

Validate GC-codes (base-31 with offset, or hex era), place caches on the 81-cell D/T Fizzy grid, chain multi-stage bearing projections into WGS84 waypoints, and cross-check puzzle finals against checker coordinates.

Details

What this tool helps you do

An offline validator for geocaching-style puzzle hunts.

GC-code engine: the 31-character alphabet 0-9ABCDEFGHJKMNPQRTVWXYZ (I, L, O, S, U excluded; typed S and O normalize to 5 and 0). Ids 0–65535 were issued as plain hexadecimal (GC0…GCFFFF); from id 65536 (GCG000) the code is base-31 with a +411120 offset — id = base31(suffix) − 411120. Verified against published vectors (GC2SOSO = GC25050 = 1585032) and the era boundary.

Projection engine: great-circle forward solution on a sphere of radius 6,371,008.8 m — φ₂ = asin(sin φ₁ cos δ + cos φ₁ sin δ cos θ), λ₂ = λ₁ + atan2(sin θ sin δ cos φ₁, cos δ − sin φ₁ sin φ₂). Legs are chained so a multi-cache stage tour resolves in one pass; every waypoint is shown in both WGS84 decimal and the N 47° 36.600′ listing format.

Checker: haversine distance plus bearing from your computed final to the checker coordinates, with a tolerance verdict and a rule-of-thumb for how far a 1° bearing error drifts.

D/T: the 81-cell Fizzy grid (D and T each 1.0–5.0 in 0.5 steps), with your cell highlighted and #81 (D5/T5) marked.

Type guidance covers multi-cache stage conventions, mystery checkers, letterbox-hybrid stamps and clue offsets (Atlas Quest lineage), EarthCache, Wherigo cartridges and Munzee QR pins (no D/T scale). Structural validation only — no live geocaching.com lookup.

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Samples

Geocache Letterbox Munzee Stage-Cache Puzzle-Hunt Coordinate Validator

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Key facts

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Use cases

Examples

1. Two-Leg Mystery Cache Projection with Checker Verification

2. Hex-Era Traditional Waypoint Offset

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