move routing files

website/src/lib/components/toolbar/tools/routing/Simplify.ts

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+import type { Coordinates, TrackPoint, TrackSegment } from "gpx";
+
+export type SimplifiedTrackPoint = { point: TrackPoint, distance?: number, zoom?: number, marker?: mapboxgl.Marker };
+
+const earthRadius = 6371008.8;
+
+export function getZoomLevelForDistance(latitude: number, distance?: number): number {
+    if (distance === undefined) {
+        return 0;
+    }
+
+    const rad = Math.PI / 180;
+    const lat = latitude * rad;
+
+    return Math.min(20, Math.max(0, Math.floor(Math.log2((earthRadius * Math.cos(lat)) / distance))));
+}
+
+export function computeAnchorPoints(segment: TrackSegment) {
+    let points = segment.trkpt;
+    let anchors = ramerDouglasPeucker(points);
+    anchors.forEach((point) => {
+        point.zoom = getZoomLevelForDistance(point.point.getLatitude(), point.distance);
+    });
+    segment._data['anchors'] = anchors;
+}
+
+export function ramerDouglasPeucker(points: TrackPoint[], epsilon: number = 50, start: number = 0, end: number = points.length - 1): SimplifiedTrackPoint[] {
+    if (points.length == 0) {
+        return [];
+    } else if (points.length == 1) {
+        return [{
+            point: points[0]
+        }];
+    }
+
+    let simplified = [{
+        point: points[start]
+    }];
+    ramerDouglasPeuckerRecursive(points, epsilon, start, end, simplified);
+    simplified.push({
+        point: points[end]
+    });
+    return simplified;
+}
+
+function ramerDouglasPeuckerRecursive(points: TrackPoint[], epsilon: number, start: number, end: number, simplified: SimplifiedTrackPoint[]) {
+    let largest = {
+        index: 0,
+        distance: 0
+    };
+
+    for (let i = start + 1; i < end; i++) {
+        let distance = crossarc(points[start].getCoordinates(), points[end].getCoordinates(), points[i].getCoordinates());
+        if (distance > largest.distance) {
+            largest.index = i;
+            largest.distance = distance;
+        }
+    }
+
+    if (largest.distance > epsilon) {
+        ramerDouglasPeuckerRecursive(points, epsilon, start, largest.index, simplified);
+        simplified.push({ point: points[largest.index], distance: largest.distance });
+        ramerDouglasPeuckerRecursive(points, epsilon, largest.index, end, simplified);
+    }
+}
+
+function crossarc(coord1: Coordinates, coord2: Coordinates, coord3: Coordinates): number {
+    // Calculates the shortest distance in meters 
+    // between an arc (defined by p1 and p2) and a third point, p3.
+    // Input lat1,lon1,lat2,lon2,lat3,lon3 in degrees.
+
+    const rad = Math.PI / 180;
+    const lat1 = coord1.lat * rad;
+    const lat2 = coord2.lat * rad;
+    const lat3 = coord3.lat * rad;
+
+    const lon1 = coord1.lon * rad;
+    const lon2 = coord2.lon * rad;
+    const lon3 = coord3.lon * rad;
+
+    // Prerequisites for the formulas
+    const bear12 = bearing(lat1, lon1, lat2, lon2);
+    const bear13 = bearing(lat1, lon1, lat3, lon3);
+    let dis13 = distance(lat1, lon1, lat3, lon3);
+
+    let diff = Math.abs(bear13 - bear12);
+    if (diff > Math.PI) {
+        diff = 2 * Math.PI - diff;
+    }
+
+    // Is relative bearing obtuse?
+    if (diff > (Math.PI / 2)) {
+        return dis13;
+    }
+
+    // Find the cross-track distance.
+    let dxt = Math.asin(Math.sin(dis13 / earthRadius) * Math.sin(bear13 - bear12)) * earthRadius;
+
+    // Is p4 beyond the arc?
+    let dis12 = distance(lat1, lon1, lat2, lon2);
+    let dis14 = Math.acos(Math.cos(dis13 / earthRadius) / Math.cos(dxt / earthRadius)) * earthRadius;
+    if (dis14 > dis12) {
+        return distance(lat2, lon2, lat3, lon3);
+    } else {
+        return Math.abs(dxt);
+    }
+}
+
+function distance(latA: number, lonA: number, latB: number, lonB: number): number {
+    // Finds the distance between two lat / lon points.
+    return Math.acos(Math.sin(latA) * Math.sin(latB) + Math.cos(latA) * Math.cos(latB) * Math.cos(lonB - lonA)) * earthRadius;
+}
+
+
+function bearing(latA: number, lonA: number, latB: number, lonB: number): number {
+    // Finds the bearing from one lat / lon point to another.
+    return Math.atan2(Math.sin(lonB - lonA) * Math.cos(latB),
+        Math.cos(latA) * Math.sin(latB) - Math.sin(latA) * Math.cos(latB) * Math.cos(lonB - lonA));
+}