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fix: use spherical polygon formula for isochrone area (Turf.js method)

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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Kerboul
2026-03-31 15:43:49 +02:00
parent 071e4f91ac
commit 70b4da8e2c
1 changed files with 7 additions and 5 deletions
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12
src/renderer/src/components/Legend.tsx
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@@ -3,16 +3,18 @@ import { useAppStore } from '../store/useAppStore'
import { formatDuration, getIsochroneColors } from '../api/ors' import { formatDuration, getIsochroneColors } from '../api/ors'
function ringAreaKm2(coords: number[][]): number { function ringAreaKm2(coords: number[][]): number {
const R = 6371
let area = 0 let area = 0
const n = coords.length const n = coords.length
for (let i = 0; i < n; i++) { for (let i = 0; i < n; i++) {
const j = (i + 1) % n const j = (i + 1) % n
area += coords[i][0] * coords[j][1] const lon1 = coords[i][0] * Math.PI / 180
area -= coords[j][0] * coords[i][1] const lat1 = coords[i][1] * Math.PI / 180
const lon2 = coords[j][0] * Math.PI / 180
const lat2 = coords[j][1] * Math.PI / 180
area += (lon2 - lon1) * (2 + Math.sin(lat1) + Math.sin(lat2))
} }
area = Math.abs(area) / 2 return Math.abs(area) * R * R / 2
const midLat = (coords.reduce((s, c) => s + c[1], 0) / coords.length) * (Math.PI / 180)
return area * 111.32 * 111.32 * Math.cos(midLat)
} }
function featureAreaKm2(f: Feature): number { function featureAreaKm2(f: Feature): number {