locate adress on map and find hail risk

2026-06-09 16:15:21 +05:30
parent 716d096fc8
commit 110790d5ae
8 changed files with 522 additions and 21 deletions
@@ -0,0 +1,95 @@
+/**
+ * hailProbability.js — conservative historical hail-risk model (spec §6).
+ *
+ * IMPORTANT framing (spec §6): the output is a HISTORICAL hazard estimate for the
+ * surrounding area, NOT a property-level forecast or guarantee. The model computes
+ * a RANGE (confidence band), not one overconfident number, and stores every
+ * assumption so the report can be defended.
+ *
+ *   lambda (λ) = deduped hail events / years
+ *   P(at least one hail event over N years) = 1 - e^(-λN)
+ *
+ * Pure function — no I/O. Fed by /api/storm-history (existing storm module, used
+ * read-only). Returns the hail_risk_snapshot shape (spec §12).
+ */
+
+function clamp(n, lo, hi) { return Math.max(lo, Math.min(hi, n)); }
+function pct(n) { return Math.round(n * 100); }
+
+/**
+ * @param {object} input
+ *   eventCount     {number}  deduped hail events observed in the window
+ *   windowYears    {number}  historical window analyzed
+ *   radiusMiles    {number}  search radius around the property
+ *   geocodeConfidence {'high'|'moderate'|'low'}
+ *   maxHailInches  {number|null}
+ *   lastEventDate  {string|null} ISO date of most recent hail event
+ *   source         {string}  human-readable data source label
+ *   generatedAt    {string}  ISO timestamp the snapshot was frozen
+ */
+export function computeHailRisk(input) {
+    const {
+        eventCount = 0,
+        windowYears = 5,
+        radiusMiles = 20,
+        geocodeConfidence = 'moderate',
+        maxHailInches = null,
+        lastEventDate = null,
+        source = 'NOAA / IEM Local Storm Reports',
+        generatedAt = new Date().toISOString(),
+    } = input || {};
+
+    const years = Math.max(1, windowYears);
+    const count = Math.max(0, eventCount);
+
+    // Annualized rate (events/year).
+    const lambda = count / years;
+
+    // Poisson confidence band using event-count standard error (√count).
+    const se = Math.sqrt(count);
+    const lambdaLow = Math.max(0, (count - se) / years);
+    const lambdaHigh = (count + se) / years;
+
+    const prob = (lam, n) => 1 - Math.exp(-lam * n);
+    const p10Base = prob(lambda, 10);
+    const p10Low = prob(lambdaLow, 10);
+    const p10High = prob(lambdaHigh, 10);
+
+    // Confidence score (0..1): sample size + window length + geocode precision.
+    const sampleScore = clamp(count / 8, 0, 1);          // ~8+ events → strong
+    const windowScore = clamp(years / 10, 0, 1);         // 10y window → full
+    const geoScore = geocodeConfidence === 'high' ? 1 : geocodeConfidence === 'moderate' ? 0.6 : 0.3;
+    const confidenceValue = +(0.4 * sampleScore + 0.3 * windowScore + 0.3 * geoScore).toFixed(2);
+    const confidenceLabel = confidenceValue >= 0.66 ? 'High' : confidenceValue >= 0.4 ? 'Moderate' : 'Low';
+
+    // Coarse exposure tier used downstream by the scoring engine (Phase 4).
+    const exposureTier = p10Base >= 0.66 ? 'high' : p10Base >= 0.33 ? 'moderate' : 'low';
+
+    return {
+        // hail_risk_snapshot fields (spec §12)
+        source,
+        windowYears: years,
+        radiusMiles,
+        eventCount: count,
+        annualRate: +lambda.toFixed(3),
+        maxHailInches,
+        lastEventDate,
+        probability10yr: { low: pct(p10Low), base: pct(p10Base), high: pct(p10High) },
+        confidence: confidenceLabel,
+        confidenceValue,
+        exposureTier,
+        generatedAt,
+
+        // Customer-facing wording (spec §6) — historical, never a forecast.
+        wording: {
+            annualRate: count === 0
+                ? 'No qualifying hail events were found in the available reports for this area.'
+                : `This area has averaged about ${lambda.toFixed(1)} observed hail event(s) per year in the available dataset.`,
+            probability: count === 0
+                ? 'There is not enough historical hail activity nearby to estimate a meaningful probability.'
+                : `Based on historical reports, the chance of at least one hail event in the next 10 years is estimated at ${pct(p10Low)}–${pct(p10High)}%, assuming future patterns resemble the past.`,
+            confidence: `Confidence: ${confidenceLabel}. This is based on county-level and nearby reports within ~${radiusMiles} miles, not a roof-specific inspection.`,
+            lastUpdated: `Storm data reflects reports through ${new Date(generatedAt).toLocaleDateString()}.`,
+        },
+    };
+}