[DATA SOURCE] Summit positions are drawn from Ordnance Survey National Grid references, converted to WGS84 latitude/longitude pairs. WGS84 is the coordinate system used by GPS devices and Strava.

[MATCHING] Each GPS coordinate sample in an imported activity is tested against every summit position in the database. The test is a horizontal distance calculation between the activity coordinate and the summit coordinate.

[RESULT] If any coordinate sample in the activity falls within 200 metres of a summit position, the ascent is marked as verified. If no sample passes within tolerance, the ascent is recorded as unverified. Both outcomes are written to the ledger.

[MULTI-SUMMIT] A single activity is audited against all summit positions simultaneously. A ridge walk passing multiple peaks will produce a separate verified ledger entry for each summit within tolerance.

[RATIONALE] A summit coordinate is a single point, but a summit is a physical area. The highest cairn on a Munro plateau may be approached from multiple angles over terrain that spans hundreds of metres. The 200-metre tolerance defines a radius within which a GPS track is accepted as having reached the summit.

[GPS ACCURACY] Consumer GPS devices operate with a typical horizontal accuracy of 3–5 metres under open sky conditions. Accuracy degrades in deep valley approaches, under tree cover, and in adverse weather. The 200-metre tolerance absorbs normal GPS drift without inflating false positives.

[FIXED] The tolerance is 200 metres. It is not configurable by the user. A uniform tolerance applies across all peak lists and all summits.

[HORIZONTAL ONLY] The tolerance is a horizontal measurement. Altitude is not used as a verification criterion. A coordinate sample at the correct horizontal position is verified regardless of its recorded altitude.

[BAROMETRIC PRIMARY] Elevation gain is calculated from barometric pressure data where present in the activity file. Barometric altitude change is derived from the relationship between atmospheric pressure and elevation. It produces more consistent vertical measurements than GPS altitude under normal field conditions.

[GPS FALLBACK] Where barometric data is absent from the activity file, GPS altitude samples are used to calculate elevation gain. GPS altitude is subject to geometric dilution and atmospheric refraction errors. This source is noted in the ledger entry.

[UNSMOOTHED] Raw samples are retained without post-processing. Northing does not apply smoothing algorithms, does not correct against a digital elevation model, and does not normalise figures between data sources.