Task group 1 of elevation-profile-hardening. New pure module
elevation-clean.ts (not yet wired — group 2 does that):
- despike(points): interpolates out isolated peak/pit spikes (opposite-sign
slope outliers both exceeding MAX_SLOPE_PERCENT=100); steep monotonic
terrain (same-sign) is never touched; per-segment, no cross-gap interp.
- filteredTotals(points): hysteresis ascent/descent (NOISE_THRESHOLD_M=5)
that suppresses sub-threshold jitter, returning {gain,loss,gainRaw,lossRaw}.
- cumulativeFilteredTotals(points): running filtered arrays for per-day
splits (day total = cumulative[end] − cumulative[start]).
DESIGN NOTE for review: the spec's task 1.2 says the zero-filtered
fallback should "report raw", but the raw sum-of-deltas re-inflates the
very jitter we remove (a ±2 m wobble sums to several metres) — directly
contradicting task 1.4's "±2 m jitter → 0 totals". Resolved toward the
stated goal: fall back to NET change (end−start), so flat wobble reads ~0
while a genuine small net climb still surfaces. gainRaw/lossRaw still
expose the raw sums.
Verified: gpx typecheck+lint clean, 108/108; full pnpm test 11/11.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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