feat(preview): add traffic signal visualization

scripts/lib/traffic-signals.js

@@ -0,0 +1,91 @@
+"use strict";
+
+const fs = require("fs");
+
+const EARTH_RADIUS = 6371008.8;
+const CURB_OFFSET_METERS = 5.2;
+const MAST_REACH_METERS = 4.5;
+
+function buildTrafficSignals(stopLines, intersections) {
+  const centers = (intersections.features || []).map((feature, index) => {
+    const point = polygonCenter(feature.geometry);
+    return { id: `intersection-${index + 1}`, point, radius: polygonRadius(feature.geometry, point) };
+  }).filter((entry) => entry.point);
+  const signals = [];
+  for (const feature of stopLines.features || []) {
+    const center = polygonCenter(feature.geometry);
+    if (!center) continue;
+    const intersection = nearestCenter(center, centers);
+    if (!intersection || metersBetween(center, intersection.point) > 32) continue;
+    const axis = roadAxis(feature.geometry, center, intersection.point);
+    if (!axis) continue;
+    // A vehicle signal belongs beyond the junction, facing back toward the
+    // approaching stop line. Use the far edge of the intersection, never the
+    // near-side stop-line area where it would read as a pedestrian signal.
+    const right = [axis[1], -axis[0]];
+    const farSide = moveMeters(intersection.point, axis, intersection.radius + 3.2);
+    // The pole is on the far-side sidewalk, not at the stop line or inside
+    // the intersection. Its mast then reaches back above the approach lanes.
+    const point = moveMeters(farSide, right, CURB_OFFSET_METERS);
+    signals.push({
+      id: `signal-${signals.length + 1}`,
+      intersectionId: intersection.id,
+      phaseGroup: signals.length % 2,
+      longitude: point[0],
+      latitude: point[1],
+      headingDegrees: Math.atan2(axis[0], axis[1]) * 180 / Math.PI,
+      mastReachMeters: MAST_REACH_METERS,
+    });
+  }
+  return { version: 1, signals };
+}
+
+function readTrafficSignals(stopLinePath, intersectionPath) {
+  return buildTrafficSignals(JSON.parse(fs.readFileSync(stopLinePath, "utf8")), JSON.parse(fs.readFileSync(intersectionPath, "utf8")));
+}
+
+function polygonCenter(geometry) {
+  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
+  if (!ring || ring.length < 4) return null;
+  const points = ring.slice(0, -1);
+  return [points.reduce((sum, point) => sum + point[0], 0) / points.length, points.reduce((sum, point) => sum + point[1], 0) / points.length];
+}
+
+function polygonRadius(geometry, center) {
+  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
+  if (!ring || !center) return 0;
+  return Math.max(...ring.slice(0, -1).map((point) => metersBetween(center, point)), 0);
+}
+
+function roadAxis(geometry, center, target) {
+  const ring = geometry?.coordinates?.[0];
+  if (!ring || ring.length < 3) return null;
+  let longest = null;
+  for (let i = 0; i < ring.length - 1; i += 1) {
+    const dx = (ring[i + 1][0] - ring[i][0]) * Math.cos(center[1] * Math.PI / 180);
+    const dy = ring[i + 1][1] - ring[i][1];
+    const length = Math.hypot(dx, dy);
+    if (!longest || length > longest.length) longest = { dx, dy, length };
+  }
+  if (!longest?.length) return null;
+  let axis = [-longest.dy / longest.length, longest.dx / longest.length];
+  const toward = [(target[0] - center[0]) * Math.cos(center[1] * Math.PI / 180), target[1] - center[1]];
+  if (axis[0] * toward[0] + axis[1] * toward[1] < 0) axis = [-axis[0], -axis[1]];
+  return axis;
+}
+
+function nearestCenter(point, centers) {
+  return centers.map((entry) => ({ ...entry, distance: metersBetween(point, entry.point) })).sort((a, b) => a.distance - b.distance)[0] || null;
+}
+
+function metersBetween(a, b) {
+  const lat = (a[1] + b[1]) / 2 * Math.PI / 180;
+  return Math.hypot((a[0] - b[0]) * Math.cos(lat), a[1] - b[1]) * Math.PI / 180 * EARTH_RADIUS;
+}
+
+function moveMeters(point, vector, meters) {
+  const scale = 180 / Math.PI / EARTH_RADIUS;
+  return [point[0] + vector[0] * meters * scale / Math.cos(point[1] * Math.PI / 180), point[1] + vector[1] * meters * scale];
+}
+
+module.exports = { buildTrafficSignals, readTrafficSignals };