feat: add trail thickness and distance settings; implement sliders in control panel and update settings context

src/components/flight-tracker.tsx

@@ -191,6 +191,8 @@ function FlightTrackerInner() {
           onHover={handleHover}
           onClick={handleClick}
           showTrails={settings.showTrails}
+          trailThickness={settings.trailThickness}
+          trailDistance={settings.trailDistance}
           showShadows={settings.showShadows}
           showAltitudeColors={settings.showAltitudeColors}
         />

src/components/map/flight-layers.tsx

@@ -9,12 +9,15 @@ import type { FlightState } from "@/lib/opensky";
 import { type TrailEntry } from "@/hooks/use-trail-history";
 import type { PickingInfo } from "@deck.gl/core";
 
-const ANIM_DURATION_MS = 30_000;
+const DEFAULT_ANIM_DURATION_MS = 30_000;
-const TELEPORT_THRESHOLD = 0.3; // degrees
+const MIN_ANIM_DURATION_MS = 8_000;
+const MAX_ANIM_DURATION_MS = 45_000;
+const TELEPORT_THRESHOLD = 0.3;
 const TRAIL_BELOW_AIRCRAFT_METERS = 20;
 const STARTUP_TRAIL_POLLS = 3;
 const STARTUP_TRAIL_STEP_SEC = 12;
 const TRACK_DAMPING = 0.18;
+const TRAIL_SMOOTHING_ITERATIONS = 3;
 
 function buildStartupFallbackTrail(f: FlightState): [number, number][] {
   if (f.longitude == null || f.latitude == null) return [];
@@ -42,10 +45,118 @@ function lerpAngle(a: number, b: number, t: number): number {
   return a + delta * t;
 }
 
+function trackFromDelta(dx: number, dy: number, fallback: number): number {
+  if (dx * dx + dy * dy < 1e-10) return fallback;
+  return ((Math.atan2(dx, dy) * 180) / Math.PI + 360) % 360;
+}
+
 function smoothStep(t: number): number {
   return t * t * (3 - 2 * t);
 }
 
+type ElevatedPoint = [number, number, number];
+
+function smoothElevatedPath(
+  points: ElevatedPoint[],
+  iterations: number = TRAIL_SMOOTHING_ITERATIONS,
+): ElevatedPoint[] {
+  if (points.length < 3 || iterations <= 0) return points;
+
+  let current = points;
+  for (let iter = 0; iter < iterations; iter++) {
+    if (current.length < 3) break;
+
+    const next: ElevatedPoint[] = [current[0]];
+    for (let i = 0; i < current.length - 1; i++) {
+      const a = current[i];
+      const b = current[i + 1];
+      next.push([
+        a[0] * 0.75 + b[0] * 0.25,
+        a[1] * 0.75 + b[1] * 0.25,
+        a[2] * 0.75 + b[2] * 0.25,
+      ]);
+      next.push([
+        a[0] * 0.25 + b[0] * 0.75,
+        a[1] * 0.25 + b[1] * 0.75,
+        a[2] * 0.25 + b[2] * 0.75,
+      ]);
+    }
+    next.push(current[current.length - 1]);
+    current = next;
+  }
+
+  return current;
+}
+
+function smoothNumericSeries(values: number[]): number[] {
+  if (values.length < 3) return values;
+  const out = [...values];
+  for (let i = 1; i < values.length - 1; i++) {
+    out[i] = values[i - 1] * 0.2 + values[i] * 0.6 + values[i + 1] * 0.2;
+  }
+  return out;
+}
+
+function smoothPlanarPath(points: [number, number][]): [number, number][] {
+  if (points.length < 3) return points;
+
+  let current = points;
+  for (let pass = 0; pass < 2; pass++) {
+    const next = [...current];
+    for (let i = 1; i < current.length - 1; i++) {
+      next[i] = [
+        current[i - 1][0] * 0.2 + current[i][0] * 0.6 + current[i + 1][0] * 0.2,
+        current[i - 1][1] * 0.2 + current[i][1] * 0.6 + current[i + 1][1] * 0.2,
+      ];
+    }
+    current = next;
+  }
+
+  return current;
+}
+
+function trimPathAheadOfAircraft(
+  points: ElevatedPoint[],
+  aircraft: ElevatedPoint,
+): ElevatedPoint[] {
+  if (points.length < 2) return [aircraft];
+
+  const px = aircraft[0];
+  const py = aircraft[1];
+
+  let bestIndex = points.length - 2;
+  let bestDistanceSq = Number.POSITIVE_INFINITY;
+  const searchStart = Math.max(0, points.length - 10);
+
+  for (let i = searchStart; i < points.length - 1; i++) {
+    const a = points[i];
+    const b = points[i + 1];
+    const dx = b[0] - a[0];
+    const dy = b[1] - a[1];
+    const denom = dx * dx + dy * dy;
+    const t =
+      denom > 1e-12
+        ? Math.max(
+            0,
+            Math.min(1, ((px - a[0]) * dx + (py - a[1]) * dy) / denom),
+          )
+        : 0;
+    const qx = a[0] + dx * t;
+    const qy = a[1] + dy * t;
+    const distSq = (px - qx) * (px - qx) + (py - qy) * (py - qy);
+
+    if (distSq < bestDistanceSq) {
+      bestDistanceSq = distSq;
+      bestIndex = i;
+    }
+  }
+
+  const trimmed = points.slice(0, bestIndex + 1);
+  trimmed.push([px, py, aircraft[2]]);
+
+  return trimmed;
+}
+
 function createAircraftAtlas(): HTMLCanvasElement {
   const size = 128;
   const canvas = document.createElement("canvas");
@@ -94,6 +205,8 @@ type FlightLayerProps = {
   onHover: (info: PickingInfo<FlightState> | null) => void;
   onClick: (info: PickingInfo<FlightState> | null) => void;
   showTrails: boolean;
+  trailThickness: number;
+  trailDistance: number;
   showShadows: boolean;
   showAltitudeColors: boolean;
 };
@@ -104,6 +217,8 @@ export function FlightLayers({
   onHover,
   onClick,
   showTrails,
+  trailThickness,
+  trailDistance,
   showShadows,
   showAltitudeColors,
 }: FlightLayerProps) {
@@ -114,11 +229,14 @@ export function FlightLayers({
   const prevSnapshotsRef = useRef<Map<string, Snapshot>>(new Map());
   const currSnapshotsRef = useRef<Map<string, Snapshot>>(new Map());
   const dataTimestampRef = useRef(0);
+  const animDurationRef = useRef(DEFAULT_ANIM_DURATION_MS);
   const animFrameRef = useRef(0);
 
   const flightsRef = useRef(flights);
   const trailsRef = useRef(trails);
   const showTrailsRef = useRef(showTrails);
+  const trailThicknessRef = useRef(trailThickness);
+  const trailDistanceRef = useRef(trailDistance);
   const showShadowsRef = useRef(showShadows);
   const showAltColorsRef = useRef(showAltitudeColors);
 
@@ -126,14 +244,15 @@ export function FlightLayers({
     flightsRef.current = flights;
     trailsRef.current = trails;
     showTrailsRef.current = showTrails;
+    trailThicknessRef.current = trailThickness;
+    trailDistanceRef.current = trailDistance;
     showShadowsRef.current = showShadows;
     showAltColorsRef.current = showAltitudeColors;
   });
 
-  // Capture current animated position as new "prev" on each data update
   useEffect(() => {
     const elapsed = performance.now() - dataTimestampRef.current;
-    const oldLinearT = Math.min(elapsed / ANIM_DURATION_MS, 1);
+    const oldLinearT = Math.min(elapsed / animDurationRef.current, 1);
     const oldAngleT = smoothStep(oldLinearT);
 
     const newPrev = new Map<string, Snapshot>();
@@ -179,7 +298,15 @@ export function FlightLayers({
       }
     }
     currSnapshotsRef.current = next;
-    dataTimestampRef.current = performance.now();
+    const now = performance.now();
+    if (dataTimestampRef.current > 0) {
+      const observedInterval = now - dataTimestampRef.current;
+      animDurationRef.current = Math.max(
+        MIN_ANIM_DURATION_MS,
+        Math.min(MAX_ANIM_DURATION_MS, observedInterval * 0.94),
+      );
+    }
+    dataTimestampRef.current = now;
   }, [flights]);
 
   const handleHover = useCallback(
@@ -232,7 +359,7 @@ export function FlightLayers({
 
       try {
         const elapsed = performance.now() - dataTimestampRef.current;
-        const rawT = elapsed / ANIM_DURATION_MS;
+        const rawT = elapsed / animDurationRef.current;
         const tPos = Math.min(rawT, 1);
         const tAngle = smoothStep(smoothStep(smoothStep(tPos)));
 
@@ -249,13 +376,12 @@ export function FlightLayers({
           const curr = currSnapshotsRef.current.get(f.icao24);
           if (!curr) return f;
 
-          // Synthesize a virtual "prev" for new flights so they slide in
           let prev = prevSnapshotsRef.current.get(f.icao24);
           if (!prev) {
             const rad = (curr.track * Math.PI) / 180;
             const spd = f.velocity ?? 200;
             const step = Math.min(
-              (spd * (ANIM_DURATION_MS / 1000)) / 111_320,
+              (spd * (animDurationRef.current / 1000)) / 111_320,
               0.015,
             );
             prev = {
@@ -269,31 +395,32 @@ export function FlightLayers({
           const dx = curr.lng - prev.lng;
           const dy = curr.lat - prev.lat;
           if (dx * dx + dy * dy > TELEPORT_THRESHOLD * TELEPORT_THRESHOLD) {
-            return f; // teleport — skip interpolation
+            return f;
           }
 
           if (rawT <= 1) {
+            const blendedTrack = lerpAngle(prev.track, curr.track, tAngle);
             return {
               ...f,
               longitude: prev.lng + dx * tPos,
               latitude: prev.lat + dy * tPos,
               baroAltitude: prev.alt + (curr.alt - prev.alt) * tPos,
-              trueTrack: lerpAngle(prev.track, curr.track, tAngle),
+              trueTrack: trackFromDelta(dx, dy, blendedTrack),
             };
           }
 
-          // Extrapolate when the next poll is delayed (velocity-continuous
-          // with the linear interpolation above)
           const heading = (curr.track * Math.PI) / 180;
           const speed = f.velocity ?? 200;
-          const extraSec = ((rawT - 1) * ANIM_DURATION_MS) / 1000;
+          const extraSec = ((rawT - 1) * animDurationRef.current) / 1000;
           const extraDeg = Math.min((speed * extraSec) / 111_320, 0.03);
+          const moveDx = Math.sin(heading) * extraDeg;
+          const moveDy = Math.cos(heading) * extraDeg;
           return {
             ...f,
-            longitude: curr.lng + Math.sin(heading) * extraDeg,
+            longitude: curr.lng + moveDx,
-            latitude: curr.lat + Math.cos(heading) * extraDeg,
+            latitude: curr.lat + moveDy,
             baroAltitude: curr.alt,
-            trueTrack: curr.track,
+            trueTrack: trackFromDelta(moveDx, moveDy, curr.track),
           };
         });
 
@@ -344,6 +471,9 @@ export function FlightLayers({
             trailData.push({
               icao24: f.icao24,
               path: startupPath,
+              altitudes: startupPath.map(
+                () => existing?.baroAltitude ?? f.baroAltitude,
+              ),
               baroAltitude: existing?.baroAltitude ?? f.baroAltitude,
             });
           }
@@ -360,14 +490,35 @@ export function FlightLayers({
               data: trailData,
               updateTriggers: { getPath: elapsed },
               getPath: (d) => {
+                const historyPoints = Math.max(
+                  2,
+                  Math.round(trailDistanceRef.current),
+                );
+                const pathSlice =
+                  d.path.length > historyPoints
+                    ? d.path.slice(d.path.length - historyPoints)
+                    : d.path;
+                const altitudeSlice =
+                  d.altitudes.length > historyPoints
+                    ? d.altitudes.slice(d.altitudes.length - historyPoints)
+                    : d.altitudes;
+                const smoothPathSlice = smoothPlanarPath(pathSlice);
+                const altitudeMeters = smoothNumericSeries(
+                  altitudeSlice.map((a) =>
+                    altitudeToElevation(a ?? d.baroAltitude),
+                  ),
+                );
+
                 const animFlight = interpolatedMap.get(d.icao24);
-                const alt = altitudeToElevation(
+                const basePath = smoothPathSlice.map((p, i) => {
-                  animFlight?.baroAltitude ?? d.baroAltitude,
+                  const pointAlt =
-                );
+                    altitudeMeters[i] ?? altitudeToElevation(d.baroAltitude);
-                const trailAlt = Math.max(0, alt - TRAIL_BELOW_AIRCRAFT_METERS);
+                  const trailAlt = Math.max(
-                const basePath = d.path.map(
+                    0,
-                  (p) => [p[0], p[1], trailAlt] as [number, number, number],
+                    pointAlt - TRAIL_BELOW_AIRCRAFT_METERS,
-                );
+                  );
+                  return [p[0], p[1], trailAlt] as [number, number, number];
+                });
                 if (
                   animFlight &&
                   animFlight.longitude != null &&
@@ -376,33 +527,33 @@ export function FlightLayers({
                 ) {
                   const ax = animFlight.longitude;
                   const ay = animFlight.latitude;
+                  const currentAlt = Math.max(
+                    0,
+                    altitudeToElevation(animFlight.baroAltitude) -
+                      TRAIL_BELOW_AIRCRAFT_METERS,
+                  );
 
-                  if (
+                  const clipped = trimPathAheadOfAircraft(basePath, [
-                    animFlight.trueTrack != null &&
+                    ax,
-                    basePath.length > STARTUP_TRAIL_POLLS + 3 &&
+                    ay,
-                    (animFlight.velocity ?? 0) > 40
+                    currentAlt,
-                  ) {
+                  ]);
-                    const heading = (animFlight.trueTrack * Math.PI) / 180;
+                  if (clipped.length < 4) return clipped;
-                    const fdx = Math.sin(heading);
+                  return smoothElevatedPath(clipped);
-                    const fdy = Math.cos(heading);
-
-                    for (let i = basePath.length - 1; i >= 0; i--) {
-                      const vx = basePath[i][0] - ax;
-                      const vy = basePath[i][1] - ay;
-                      if (vx * fdx + vy * fdy > 0) {
-                        basePath[i] = [ax, ay, trailAlt];
-                      } else {
-                        break;
-                      }
-                    }
-                  }
-
-                  basePath[basePath.length - 1] = [ax, ay, trailAlt];
                 }
-                return basePath;
+                if (basePath.length < 4) return basePath;
+                return smoothElevatedPath(basePath);
               },
               getColor: (d) => {
-                const len = d.path.length;
+                const historyPoints = Math.max(
+                  2,
+                  Math.round(trailDistanceRef.current),
+                );
+                const visibleLen = Math.min(d.path.length, historyPoints);
+                const len =
+                  visibleLen < 4
+                    ? visibleLen
+                    : visibleLen * 2 ** TRAIL_SMOOTHING_ITERATIONS;
                 const base = altColors
                   ? altitudeToColor(d.baroAltitude)
                   : defaultColor;
@@ -417,10 +568,10 @@ export function FlightLayers({
                   ];
                 }) as [number, number, number, number][];
               },
-              getWidth: 3,
+              getWidth: trailThicknessRef.current,
               widthUnits: "pixels",
-              widthMinPixels: 2,
+              widthMinPixels: Math.max(1, trailThicknessRef.current * 0.6),
-              widthMaxPixels: 6,
+              widthMaxPixels: Math.max(2, trailThicknessRef.current * 1.8),
               billboard: true,
               capRounded: true,
               jointRounded: true,

src/components/ui/control-panel.tsx

@@ -638,6 +638,10 @@ const ORBIT_SPEED_PRESETS = [
 const ORBIT_SPEED_MIN = 0.02;
 const ORBIT_SPEED_MAX = 0.5;
 const ORBIT_SNAP_THRESHOLD = 0.025;
+const TRAIL_THICKNESS_MIN = 1;
+const TRAIL_THICKNESS_MAX = 8;
+const TRAIL_DISTANCE_MIN = 12;
+const TRAIL_DISTANCE_MAX = 100;
 
 const ORBIT_DIRECTIONS: { label: string; value: OrbitDirection }[] = [
   { label: "Clockwise", value: "clockwise" },
@@ -645,7 +649,7 @@ const ORBIT_DIRECTIONS: { label: string; value: OrbitDirection }[] = [
 ];
 
 function SettingsContent() {
-  const { settings, update } = useSettings();
+  const { settings, update, reset } = useSettings();
 
   return (
     <ScrollArea className="h-full">
@@ -683,6 +687,18 @@ function SettingsContent() {
           checked={settings.showTrails}
           onChange={(v) => update("showTrails", v)}
         />
+        {settings.showTrails && (
+          <>
+            <TrailThicknessSlider
+              value={settings.trailThickness}
+              onChange={(v) => update("trailThickness", v)}
+            />
+            <TrailDistanceSlider
+              value={settings.trailDistance}
+              onChange={(v) => update("trailDistance", v)}
+            />
+          </>
+        )}
         <SettingRow
           icon={<Layers className="h-4 w-4" />}
           title="Ground shadows"
@@ -697,6 +713,16 @@ function SettingsContent() {
           checked={settings.showAltitudeColors}
           onChange={(v) => update("showAltitudeColors", v)}
         />
+
+        <div className="px-3 pt-2">
+          <button
+            type="button"
+            onClick={reset}
+            className="inline-flex h-8 items-center justify-center rounded-lg px-3 text-[12px] font-medium text-white/65 ring-1 ring-white/10 transition-colors hover:bg-white/5 hover:text-white/85"
+          >
+            Reset to defaults
+          </button>
+        </div>
       </div>
     </ScrollArea>
   );
@@ -771,6 +797,74 @@ function OrbitSpeedSlider({
   );
 }
 
+function TrailThicknessSlider({
+  value,
+  onChange,
+}: {
+  value: number;
+  onChange: (v: number) => void;
+}) {
+  return (
+    <div className="flex w-full items-center gap-3.5 rounded-xl px-3 py-2.5 text-left">
+      <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-lg bg-white/5 text-white/35 ring-1 ring-white/6">
+        <Layers className="h-4 w-4" />
+      </div>
+      <div className="flex flex-1 min-w-0 flex-col gap-2">
+        <div className="flex items-center justify-between">
+          <p className="text-[13px] font-medium text-white/80">
+            Trail thickness
+          </p>
+          <span className="text-[11px] font-semibold text-white/40 tabular-nums">
+            {value.toFixed(1)} px
+          </span>
+        </div>
+        <Slider
+          min={TRAIL_THICKNESS_MIN}
+          max={TRAIL_THICKNESS_MAX}
+          step={0.1}
+          value={[value]}
+          onValueChange={(vals) => onChange(vals[0])}
+          aria-label="Trail thickness"
+        />
+      </div>
+    </div>
+  );
+}
+
+function TrailDistanceSlider({
+  value,
+  onChange,
+}: {
+  value: number;
+  onChange: (v: number) => void;
+}) {
+  return (
+    <div className="flex w-full items-center gap-3.5 rounded-xl px-3 py-2.5 text-left">
+      <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-lg bg-white/5 text-white/35 ring-1 ring-white/6">
+        <Route className="h-4 w-4" />
+      </div>
+      <div className="flex flex-1 min-w-0 flex-col gap-2">
+        <div className="flex items-center justify-between">
+          <p className="text-[13px] font-medium text-white/80">
+            Trail distance
+          </p>
+          <span className="text-[11px] font-semibold text-white/40 tabular-nums">
+            {value} pts
+          </span>
+        </div>
+        <Slider
+          min={TRAIL_DISTANCE_MIN}
+          max={TRAIL_DISTANCE_MAX}
+          step={1}
+          value={[value]}
+          onValueChange={(vals) => onChange(vals[0])}
+          aria-label="Trail distance"
+        />
+      </div>
+    </div>
+  );
+}
+
 function SettingRow({
   icon,
   title,

src/hooks/use-settings.tsx

@@ -18,15 +18,43 @@ export type Settings = {
   orbitSpeed: number;
   orbitDirection: OrbitDirection;
   showTrails: boolean;
+  trailThickness: number;
+  trailDistance: number;
   showShadows: boolean;
   showAltitudeColors: boolean;
 };
 
+const TRAIL_THICKNESS_MIN = 1;
+const TRAIL_THICKNESS_MAX = 8;
+const TRAIL_DISTANCE_MIN = 12;
+const TRAIL_DISTANCE_MAX = 100;
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.max(min, Math.min(max, value));
+}
+
+function normalizeSettings(input: Settings): Settings {
+  return {
+    ...input,
+    orbitSpeed: clamp(input.orbitSpeed, 0.02, 0.5),
+    trailThickness: clamp(
+      input.trailThickness,
+      TRAIL_THICKNESS_MIN,
+      TRAIL_THICKNESS_MAX,
+    ),
+    trailDistance: Math.round(
+      clamp(input.trailDistance, TRAIL_DISTANCE_MIN, TRAIL_DISTANCE_MAX),
+    ),
+  };
+}
+
 const DEFAULT_SETTINGS: Settings = {
   autoOrbit: true,
   orbitSpeed: 0.06,
   orbitDirection: "clockwise",
   showTrails: true,
+  trailThickness: 2,
+  trailDistance: 40,
   showShadows: true,
   showAltitudeColors: true,
 };
@@ -50,6 +78,14 @@ function isValidSettings(obj: unknown): obj is Settings {
     (s.orbitDirection === "clockwise" ||
       s.orbitDirection === "counter-clockwise") &&
     typeof s.showTrails === "boolean" &&
+    typeof s.trailThickness === "number" &&
+    Number.isFinite(s.trailThickness) &&
+    s.trailThickness >= TRAIL_THICKNESS_MIN &&
+    s.trailThickness <= TRAIL_THICKNESS_MAX &&
+    typeof s.trailDistance === "number" &&
+    Number.isFinite(s.trailDistance) &&
+    s.trailDistance >= TRAIL_DISTANCE_MIN &&
+    s.trailDistance <= TRAIL_DISTANCE_MAX &&
     typeof s.showShadows === "boolean" &&
     typeof s.showAltitudeColors === "boolean"
   );
@@ -62,7 +98,6 @@ function loadSettings(): Settings {
     if (!raw) return DEFAULT_SETTINGS;
     const envelope: StorageEnvelope = JSON.parse(raw);
     if (envelope.v !== STORAGE_VERSION || !isValidSettings(envelope.data)) {
-      // Merge salvageable keys with defaults
       const merged = { ...DEFAULT_SETTINGS };
       if (typeof envelope.data === "object" && envelope.data !== null) {
         const d = envelope.data as Record<string, unknown>;
@@ -72,9 +107,9 @@ function loadSettings(): Settings {
           }
         }
       }
-      return merged;
+      return normalizeSettings(merged);
     }
-    return { ...DEFAULT_SETTINGS, ...envelope.data };
+    return normalizeSettings({ ...DEFAULT_SETTINGS, ...envelope.data });
   } catch {
     return DEFAULT_SETTINGS;
   }
@@ -93,6 +128,7 @@ function saveSettings(settings: Settings): void {
 type SettingsContextValue = {
   settings: Settings;
   update: <K extends keyof Settings>(key: K, value: Settings[K]) => void;
+  reset: () => void;
 };
 
 const SettingsContext = createContext<SettingsContextValue | null>(null);
@@ -138,14 +174,18 @@ export function SettingsProvider({ children }: { children: ReactNode }) {
     <K extends keyof Settings>(key: K, value: Settings[K]) => {
       setOverride((prev) => {
         const base = prev ?? getSettingsSnapshot();
-        return { ...base, [key]: value };
+        return normalizeSettings({ ...base, [key]: value });
       });
     },
     [],
   );
 
+  const reset = useCallback(() => {
+    setOverride({ ...DEFAULT_SETTINGS });
+  }, []);
+
   return (
-    <SettingsContext.Provider value={{ settings, update }}>
+    <SettingsContext.Provider value={{ settings, update, reset }}>
       {children}
     </SettingsContext.Provider>
   );

src/hooks/use-trail-history.ts

@@ -5,73 +5,44 @@ import type { FlightState } from "@/lib/opensky";
 
 type Position = [lng: number, lat: number];
 
+type TrailPoint = {
+  position: Position;
+  baroAltitude: number | null;
+};
+
 export type TrailEntry = {
   icao24: string;
   path: Position[];
+  altitudes: Array<number | null>;
   baroAltitude: number | null;
 };
 
 const MAX_POINTS = 40;
 const JUMP_THRESHOLD_DEG = 0.3;
-export const SAMPLES_PER_SEGMENT = 16;
 const HISTORICAL_BOOTSTRAP_POLLS = 3;
 const HISTORICAL_BOOTSTRAP_STEP_SEC = 12;
 const BOOTSTRAP_UPDATES = 3;
+const ALTITUDE_RECENT_WINDOW = 6;
+const ALTITUDE_SOFT_STEP_METERS = 500;
+const ALTITUDE_HARD_STEP_METERS = 12_000;
+const ALTITUDE_OUTLIER_BASE_METERS = 1_200;
+const ALTITUDE_OUTLIER_SCALE = 3;
+const ALTITUDE_SMOOTHING_ALPHA_TRUSTED = 0.9;
+const ALTITUDE_SMOOTHING_ALPHA_GUARDED = 0.5;
 
-// Centripetal Catmull-Rom spline (Barry-Goldman algorithm, α = 0.5).
+type AltitudeState = {
-// Produces smooth C1 curves that pass through every control point.
+  filtered: number | null;
-function catmullRomSmooth(
+  recent: number[];
-  points: Position[],
+  outlierStreak: number;
-  samplesPerSegment: number = SAMPLES_PER_SEGMENT,
+};
-): Position[] {
-  if (points.length < 3) return [...points];
 
-  const result: Position[] = [points[0]];
+function median(values: number[]): number {
-
+  if (values.length === 0) return 0;
-  for (let i = 0; i < points.length - 1; i++) {
+  const sorted = [...values].sort((a, b) => a - b);
-    const p0 = points[Math.max(0, i - 1)];
+  const middle = Math.floor(sorted.length / 2);
-    const p1 = points[i];
+  return sorted.length % 2 === 0
-    const p2 = points[i + 1];
+    ? (sorted[middle - 1] + sorted[middle]) / 2
-    const p3 = points[Math.min(points.length - 1, i + 2)];
+    : sorted[middle];
-
-    const d01 = Math.pow(Math.hypot(p1[0] - p0[0], p1[1] - p0[1]), 0.5) || 1e-6;
-    const d12 = Math.pow(Math.hypot(p2[0] - p1[0], p2[1] - p1[1]), 0.5) || 1e-6;
-    const d23 = Math.pow(Math.hypot(p3[0] - p2[0], p3[1] - p2[1]), 0.5) || 1e-6;
-
-    const t0 = 0;
-    const t1 = d01;
-    const t2 = t1 + d12;
-    const t3 = t2 + d23;
-
-    for (let s = 1; s <= samplesPerSegment; s++) {
-      const t = t1 + (t2 - t1) * (s / samplesPerSegment);
-
-      const a1x =
-        ((t1 - t) / (t1 - t0)) * p0[0] + ((t - t0) / (t1 - t0)) * p1[0];
-      const a1y =
-        ((t1 - t) / (t1 - t0)) * p0[1] + ((t - t0) / (t1 - t0)) * p1[1];
-      const a2x =
-        ((t2 - t) / (t2 - t1)) * p1[0] + ((t - t1) / (t2 - t1)) * p2[0];
-      const a2y =
-        ((t2 - t) / (t2 - t1)) * p1[1] + ((t - t1) / (t2 - t1)) * p2[1];
-      const a3x =
-        ((t3 - t) / (t3 - t2)) * p2[0] + ((t - t2) / (t3 - t2)) * p3[0];
-      const a3y =
-        ((t3 - t) / (t3 - t2)) * p2[1] + ((t - t2) / (t3 - t2)) * p3[1];
-
-      const b1x = ((t2 - t) / (t2 - t0)) * a1x + ((t - t0) / (t2 - t0)) * a2x;
-      const b1y = ((t2 - t) / (t2 - t0)) * a1y + ((t - t0) / (t2 - t0)) * a2y;
-      const b2x = ((t3 - t) / (t3 - t1)) * a2x + ((t - t1) / (t3 - t1)) * a3x;
-      const b2y = ((t3 - t) / (t3 - t1)) * a2y + ((t - t1) / (t3 - t1)) * a3y;
-
-      const cx = ((t2 - t) / (t2 - t1)) * b1x + ((t - t1) / (t2 - t1)) * b2x;
-      const cy = ((t2 - t) / (t2 - t1)) * b1y + ((t - t1) / (t2 - t1)) * b2y;
-
-      result.push([cx, cy]);
-    }
-  }
-
-  return result;
 }
 
 function synthesizeHistoricalPolls(f: FlightState): Position[] {
@@ -96,10 +67,58 @@ function synthesizeHistoricalPolls(f: FlightState): Position[] {
 }
 
 class TrailStore {
-  private trails = new Map<string, Position[]>();
+  private trails = new Map<string, TrailPoint[]>();
+  private altitudeStates = new Map<string, AltitudeState>();
   private seen = new Set<string>();
   private bootstrapUpdatesRemaining = BOOTSTRAP_UPDATES;
 
+  private filterAltitude(id: string, rawAltitude: number | null): number | null {
+    if (rawAltitude == null) return null;
+
+    const state =
+      this.altitudeStates.get(id) ??
+      ({ filtered: null, recent: [], outlierStreak: 0 } as AltitudeState);
+
+    if (state.filtered == null) {
+      state.filtered = rawAltitude;
+      state.recent.push(rawAltitude);
+      this.altitudeStates.set(id, state);
+      return rawAltitude;
+    }
+
+    const med = median(state.recent);
+    const absoluteDeviations = state.recent.map((x) => Math.abs(x - med));
+    const mad = median(absoluteDeviations);
+    const outlierThreshold =
+      ALTITUDE_OUTLIER_BASE_METERS + ALTITUDE_OUTLIER_SCALE * Math.max(120, mad);
+
+    const isOutlier = Math.abs(rawAltitude - med) > outlierThreshold;
+    state.outlierStreak = isOutlier ? state.outlierStreak + 1 : 0;
+    const trustedTarget = !isOutlier || state.outlierStreak >= 2;
+    const maxStep = trustedTarget
+      ? ALTITUDE_HARD_STEP_METERS
+      : ALTITUDE_SOFT_STEP_METERS;
+    const alpha = trustedTarget
+      ? ALTITUDE_SMOOTHING_ALPHA_TRUSTED
+      : ALTITUDE_SMOOTHING_ALPHA_GUARDED;
+
+    const delta = rawAltitude - state.filtered;
+    const clampedDelta = Math.max(
+      -maxStep,
+      Math.min(maxStep, delta),
+    );
+
+    const filtered = state.filtered + clampedDelta * alpha;
+    state.filtered = filtered;
+    state.recent.push(filtered);
+    if (state.recent.length > ALTITUDE_RECENT_WINDOW) {
+      state.recent.splice(0, state.recent.length - ALTITUDE_RECENT_WINDOW);
+    }
+
+    this.altitudeStates.set(id, state);
+    return filtered;
+  }
+
   update(flights: FlightState[]): TrailEntry[] {
     const current = new Set<string>();
     let processedFlightCount = 0;
@@ -109,13 +128,22 @@ class TrailStore {
       processedFlightCount += 1;
       const id = f.icao24;
       current.add(id);
+      const filteredAltitude = this.filterAltitude(id, f.baroAltitude);
 
-      const pos: Position = [f.longitude, f.latitude];
+      const pos: TrailPoint = {
+        position: [f.longitude, f.latitude],
+        baroAltitude: filteredAltitude,
+      };
       let trail = this.trails.get(id);
 
       if (!trail) {
         trail =
-          this.bootstrapUpdatesRemaining > 0 ? synthesizeHistoricalPolls(f) : [];
+          this.bootstrapUpdatesRemaining > 0
+            ? synthesizeHistoricalPolls(f).map((position) => ({
+                position,
+                baroAltitude: filteredAltitude,
+              }))
+            : [];
         this.trails.set(id, trail);
       }
 
@@ -124,9 +152,9 @@ class TrailStore {
         continue;
       }
 
-      const last = trail[trail.length - 1];
+      const last = trail[trail.length - 1].position;
-      const dx = pos[0] - last[0];
+      const dx = pos.position[0] - last[0];
-      const dy = pos[1] - last[1];
+      const dy = pos.position[1] - last[1];
       if (dx * dx + dy * dy > JUMP_THRESHOLD_DEG * JUMP_THRESHOLD_DEG) {
         trail.length = 0;
       }
@@ -138,7 +166,10 @@ class TrailStore {
     }
 
     for (const id of this.seen) {
-      if (!current.has(id)) this.trails.delete(id);
+      if (!current.has(id)) {
+        this.trails.delete(id);
+        this.altitudeStates.delete(id);
+      }
     }
     this.seen = current;
 
@@ -150,10 +181,14 @@ class TrailStore {
     for (const f of flights) {
       const trail = this.trails.get(f.icao24);
       if (trail && trail.length >= 2) {
+        const path = trail.map((p) => p.position);
+        const altitudes = trail.map((p) => p.baroAltitude);
+
         result.push({
           icao24: f.icao24,
-          path: trail.length >= 5 ? catmullRomSmooth(trail) : [...trail],
+          path: [...path],
-          baroAltitude: f.baroAltitude,
+          altitudes,
+          baroAltitude: altitudes[altitudes.length - 1] ?? null,
         });
       }
     }