Add terrain/elevation data fetching (Doku 3.9)

Rundet das Altitude-Tab um ein reales Gelaendeprofil ab, damit sichtbar
wird, ob die geplante Flughoehe ausreichend Bodenabstand haelt:

- domain/mission/terrain_math.dart: reine Sampling-/Geometrie-Funktionen
  (routeKeyForTerrain fuer Caching, distanzbasiertes Sampling alle 30m,
  lineare Sollhoehen-Interpolation, terrainDangerRanges fuer Abschnitte
  mit < 10m Bodenabstand) - unabhaengig testbar ohne Netzwerk/UI.
- services/terrain/terrain_service.dart: laedt AWS-Terrarium-PNG-Kacheln
  (elevation-tiles-prod, zoom 13) und dekodiert sie ueber dart:ui
  (instantiateImageCodec/toByteData), ohne zusaetzliches Bildpaket.
  Elevation = R*256 + G + B/256 - 32768 pro Pixel; Kacheln werden pro
  Route nur einmal geladen (nach Kachel gruppierte Sample-Punkte).
- ui/providers/terrain_provider.dart: cached das geladene Profil ueber
  routeKeyForTerrain - reine Werteaenderungen (Hoehe/Speed) loesen keinen
  erneuten Kachel-Download aus, nur eine tatsaechliche Ortsverschiebung.
- ui/widgets/full_value_chart.dart: _paintDangerBands/_paintTerrain
  zeichnen rote Gefahrenbaender bzw. die braune Gelaende-Flaeche, in der
  gleichen Reihenfolge wie im HTML-Demonstrator (dangerHtml, grid,
  terrainHtml, dann Soll-Kurve obenauf).
- ui/widgets/waypoint_list_panel.dart: triggert ensureFor() beim
  Wechsel auf den Altitude-Tab sowie bei Routenaenderungen waehrend
  dieser aktiv ist (ref.listenManual auf currentMissionProvider).

Getestet: 13 neue Unit-Tests fuer die reine Geometrie/Sampling-Logik,
3 Service-Tests mit einer zur Testzeit synthetisch erzeugten PNG
(dart:ui-Encoding, keine Testasset-Datei noetig). Alle 80 Tests sowie
flutter analyze bestehen. Manuell auf dem Pixel_10a-Emulator verifiziert:
Altitude-Tab zeigt das reale Amsterdam-Gelaendeprofil (nahe Meereshoehe)
korrekt als Flaeche unter der Sollhoehen-Linie.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/lib/domain/mission/terrain_math.dart

@@ -0,0 +1,159 @@
+import 'package:latlong2/latlong.dart';
+
+import '../waypoint/flat_waypoint_list.dart';
+
+/// Distanzbasierte Sampling-Strategie (Doku 3.9): alle 30 m, mind. 10 /
+/// max. 2000 Samples - unabhaengig von der Anzahl Wegpunkte, damit auch
+/// lange Geradenstuecke zwischen zwei Wegpunkten ein glattes Profil
+/// bekommen.
+const terrainSampleSpacingM = 30.0;
+const terrainMaxSamples = 2000;
+
+/// Mindest-Bodenabstand, unterhalb dessen ein Streckenabschnitt als nicht
+/// sicher markiert wird (Doku 3.9/3.10).
+const minTerrainClearanceM = 10.0;
+
+const _distance = Distance(roundResult: false);
+
+/// Eindeutiger Schluessel fuer die aktuelle Route (Rundung auf 5
+/// Nachkommastellen wie bei der Wind-Interpolation) - aendert sich, sobald
+/// sich ein Wegpunkt verschiebt, nicht aber bei reinen Hoehen-/
+/// Geschwindigkeitsaenderungen. Damit laesst sich ein bereits geladenes
+/// Terrainprofil cachen, analog routeKeyForTerrain() im HTML-Demonstrator.
+String routeKeyForTerrain(List<Waypoint> waypoints) {
+  return waypoints
+      .map((w) => '${w.lat.toStringAsFixed(5)},${w.lon.toStringAsFixed(5)}')
+      .join('|');
+}
+
+/// Ein Streckenpunkt in [distanceM] Entfernung vom ersten Wegpunkt.
+class RouteSamplePoint {
+  const RouteSamplePoint({required this.distanceM, required this.point});
+
+  final double distanceM;
+  final LatLng point;
+}
+
+List<double> _cumulativeDistances(List<Waypoint> waypoints) {
+  final cum = <double>[0];
+  for (var i = 1; i < waypoints.length; i++) {
+    cum.add(cum[i - 1] +
+        _distance(
+          LatLng(waypoints[i - 1].lat, waypoints[i - 1].lon),
+          LatLng(waypoints[i].lat, waypoints[i].lon),
+        ));
+  }
+  return cum;
+}
+
+/// Wie viele Samples fuer die aktuelle Routenlaenge angemessen sind
+/// (Doku 3.9), analog `Math.min(Math.max(Math.ceil(totalRouteDist /
+/// TERRAIN_SAMPLE_SPACING), 10), TERRAIN_MAX_SAMPLES)`.
+int sampleCountFor(List<Waypoint> waypoints) {
+  if (waypoints.length < 2) return 0;
+  final cum = _cumulativeDistances(waypoints);
+  final total = cum.last;
+  final raw = (total / terrainSampleSpacingM).ceil();
+  return raw.clamp(10, terrainMaxSamples);
+}
+
+/// Sampelt [numSamples] + 1 Punkte gleichmaessig nach zurueckgelegter
+/// Strecke (nicht nach Wegpunktindex) - analog sampleRouteLatLng() im
+/// HTML-Demonstrator.
+List<RouteSamplePoint> sampleRouteByDistance(
+  List<Waypoint> waypoints,
+  int numSamples,
+) {
+  final n = waypoints.length;
+  if (n < 2 || numSamples <= 0) return [];
+  final cum = _cumulativeDistances(waypoints);
+  final total = cum.last == 0 ? 1.0 : cum.last;
+
+  final points = <RouteSamplePoint>[];
+  for (var s = 0; s <= numSamples; s++) {
+    final target = (s / numSamples) * total;
+    var legIdx = 0;
+    while (legIdx < n - 2 && cum[legIdx + 1] < target) {
+      legIdx++;
+    }
+    final legStart = cum[legIdx];
+    final legEnd = cum[legIdx + 1];
+    final frac = legEnd > legStart ? (target - legStart) / (legEnd - legStart) : 0.0;
+    final a = waypoints[legIdx];
+    final b = waypoints[legIdx + 1];
+    points.add(RouteSamplePoint(
+      distanceM: target,
+      point: LatLng(
+        a.lat + (b.lat - a.lat) * frac,
+        a.lon + (b.lon - a.lon) * frac,
+      ),
+    ));
+  }
+  return points;
+}
+
+/// Ein Gelaende-Sample in [distanceM] Streckenentfernung; [elevationRelM]
+/// ist relativ zum ersten gueltigen Sample der Route (nicht absolut ueber
+/// dem Meeresspiegel) - null, wo die Kachel nicht geladen werden konnte.
+class TerrainSamplePoint {
+  const TerrainSamplePoint({required this.distanceM, this.elevationRelM});
+
+  final double distanceM;
+  final double? elevationRelM;
+}
+
+/// Ein geladenes Gelaendeprofil, an [routeKey] gebunden - passt der
+/// aktuelle routeKeyForTerrain()-Wert nicht mehr, muss neu geladen werden.
+class TerrainProfile {
+  const TerrainProfile({required this.routeKey, required this.points});
+
+  final String routeKey;
+  final List<TerrainSamplePoint> points;
+}
+
+/// Lineare Interpolation der geplanten (Soll-)Hoehe an einer beliebigen
+/// Streckenposition - analog plannedAltAt() im HTML-Demonstrator.
+double plannedAltitudeAt(List<Waypoint> waypoints, double distanceM) {
+  final n = waypoints.length;
+  if (n == 1) return waypoints.first.altitudeM;
+  final cum = _cumulativeDistances(waypoints);
+  if (distanceM <= cum.first) return waypoints.first.altitudeM;
+  if (distanceM >= cum.last) return waypoints.last.altitudeM;
+  for (var k = 0; k < n - 1; k++) {
+    if (distanceM >= cum[k] && distanceM <= cum[k + 1]) {
+      final span = cum[k + 1] - cum[k];
+      final frac = span > 0 ? (distanceM - cum[k]) / span : 0.0;
+      return waypoints[k].altitudeM +
+          (waypoints[k + 1].altitudeM - waypoints[k].altitudeM) * frac;
+    }
+  }
+  return waypoints.last.altitudeM;
+}
+
+/// Streckenabschnitte, an denen der Bodenabstand [minTerrainClearanceM]
+/// unterschreitet (als [start, end]-Distanzpaare) - analog
+/// checkTerrainClearance() im HTML-Demonstrator.
+List<(double, double)> terrainDangerRanges(
+  List<Waypoint> waypoints,
+  TerrainProfile profile,
+) {
+  if (waypoints.length < 2) return [];
+  final ranges = <(double, double)>[];
+  double? rangeStart;
+  for (final p in profile.points) {
+    final elevRel = p.elevationRelM;
+    if (elevRel == null) continue;
+    final clearance = plannedAltitudeAt(waypoints, p.distanceM) - elevRel;
+    final bad = clearance < minTerrainClearanceM;
+    if (bad) {
+      rangeStart ??= p.distanceM;
+    } else if (rangeStart != null) {
+      ranges.add((rangeStart, p.distanceM));
+      rangeStart = null;
+    }
+  }
+  if (rangeStart != null) {
+    ranges.add((rangeStart, profile.points.last.distanceM));
+  }
+  return ranges;
+}

app/lib/services/terrain/terrain_service.dart

@@ -0,0 +1,120 @@
+import 'dart:math' as math;
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:http/http.dart' as http;
+
+import '../../domain/mission/terrain_math.dart';
+import '../../domain/waypoint/flat_waypoint_list.dart';
+
+/// Hoehendaten ueber AWS-Terrarium-Kacheln (Doku 3.9): PNG-kodierte
+/// Rasterkacheln im selben z/x/y-Schema wie die OSM-Basiskarte, jeder
+/// Pixel kodiert eine absolute Hoehe in den RGB-Kanaelen (Terrarium-Format:
+/// `elevation = R*256 + G + B/256 - 32768`).
+class TerrainService {
+  TerrainService({http.Client? client}) : _client = client ?? http.Client();
+
+  final http.Client _client;
+
+  static const _tileUrlTemplate =
+      'https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png';
+  static const _zoom = 13;
+  static const _tileSize = 256;
+
+  /// Kachelkoordinate plus Pixelposition innerhalb der Kachel fuer einen
+  /// Punkt - analog lngLatToTilePixel() im HTML-Demonstrator.
+  ({int tx, int ty, int px, int py}) _tilePixelFor(double lat, double lon) {
+    final n = math.pow(2, _zoom).toDouble();
+    final x = (lon + 180) / 360 * n;
+    final latRad = lat * math.pi / 180;
+    final y =
+        (1 - math.log(math.tan(latRad) + 1 / math.cos(latRad)) / math.pi) /
+            2 *
+            n;
+    final tx = x.floor();
+    final ty = y.floor();
+    final px = ((x - tx) * _tileSize).floor().clamp(0, _tileSize - 1);
+    final py = ((y - ty) * _tileSize).floor().clamp(0, _tileSize - 1);
+    return (tx: tx, ty: ty, px: px, py: py);
+  }
+
+  Future<Uint8List?> _fetchTileRgba(int tx, int ty) async {
+    final url = _tileUrlTemplate
+        .replaceAll('{z}', '$_zoom')
+        .replaceAll('{x}', '$tx')
+        .replaceAll('{y}', '$ty');
+    try {
+      final response = await _client.get(Uri.parse(url));
+      if (response.statusCode != 200) return null;
+      final codec = await ui.instantiateImageCodec(response.bodyBytes);
+      final frame = await codec.getNextFrame();
+      final byteData =
+          await frame.image.toByteData(format: ui.ImageByteFormat.rawRgba);
+      return byteData?.buffer.asUint8List();
+    } catch (_) {
+      // CORS-Aequivalent/Kachel fehlt/Decodierfehler: Punkt bleibt null,
+      // kein Absturz (analog dem try/catch um ctx.getImageData() im
+      // HTML-Demonstrator).
+      return null;
+    }
+  }
+
+  double? _elevationAt(Uint8List rgba, int px, int py) {
+    final offset = (py * _tileSize + px) * 4;
+    if (offset + 2 >= rgba.length) return null;
+    final r = rgba[offset];
+    final g = rgba[offset + 1];
+    final b = rgba[offset + 2];
+    return (r * 256 + g + b / 256) - 32768;
+  }
+
+  /// Laedt das Gelaendeprofil fuer die aktuelle Route (Doku 3.9): sampelt
+  /// distanzbasiert, gruppiert die Sample-Punkte nach Kachel (jede Kachel
+  /// wird nur einmal geladen) und macht die Hoehe relativ zum ersten
+  /// gueltigen Sample. Null, wenn keine einzige Kachel geladen werden
+  /// konnte oder die Route weniger als zwei Wegpunkte hat.
+  Future<TerrainProfile?> fetchProfile(List<Waypoint> waypoints) async {
+    if (waypoints.length < 2) return null;
+
+    final numSamples = sampleCountFor(waypoints);
+    final samples = sampleRouteByDistance(waypoints, numSamples);
+    if (samples.isEmpty) return null;
+
+    final tileGroups = <String, List<int>>{};
+    final tileCoords = <String, (int, int)>{};
+    final pixelForIndex = <int, (int, int)>{};
+    for (var i = 0; i < samples.length; i++) {
+      final t = _tilePixelFor(samples[i].point.latitude, samples[i].point.longitude);
+      final key = '${t.tx}_${t.ty}';
+      tileGroups.putIfAbsent(key, () => []).add(i);
+      tileCoords[key] = (t.tx, t.ty);
+      pixelForIndex[i] = (t.px, t.py);
+    }
+
+    final elevations = List<double?>.filled(samples.length, null);
+    await Future.wait(tileGroups.entries.map((entry) async {
+      final (tx, ty) = tileCoords[entry.key]!;
+      final rgba = await _fetchTileRgba(tx, ty);
+      if (rgba == null) return;
+      for (final idx in entry.value) {
+        final (px, py) = pixelForIndex[idx]!;
+        elevations[idx] = _elevationAt(rgba, px, py);
+      }
+    }));
+
+    final validIdx = elevations.indexWhere((e) => e != null);
+    if (validIdx == -1) return null;
+    final home = elevations[validIdx]!;
+
+    return TerrainProfile(
+      routeKey: routeKeyForTerrain(waypoints),
+      points: [
+        for (var i = 0; i < samples.length; i++)
+          TerrainSamplePoint(
+            distanceM: samples[i].distanceM,
+            elevationRelM: elevations[i] != null ? elevations[i]! - home : null,
+          ),
+      ],
+    );
+  }
+}

app/lib/ui/providers/terrain_provider.dart

@@ -0,0 +1,54 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../domain/mission/terrain_math.dart';
+import '../../domain/waypoint/flat_waypoint_list.dart';
+import '../../services/terrain/terrain_service.dart';
+
+final terrainServiceProvider = Provider<TerrainService>((ref) => TerrainService());
+
+/// Zustand des Gelaendeprofils fuer die aktuelle Route (Doku 3.9).
+class TerrainState {
+  const TerrainState({this.profile, this.loading = false});
+
+  final TerrainProfile? profile;
+  final bool loading;
+
+  TerrainState copyWith({TerrainProfile? profile, bool? loading}) {
+    return TerrainState(
+      profile: profile ?? this.profile,
+      loading: loading ?? this.loading,
+    );
+  }
+}
+
+/// Laedt das Gelaendeprofil nur, wenn sich die Route (routeKeyForTerrain)
+/// seit dem letzten Laden geaendert hat - analog dem
+/// `terrainSamples.routeKey === key`-Cache im HTML-Demonstrator. Ein
+/// reiner Werte-/Aktionswechsel (Hoehe, Geschwindigkeit) an bestehenden
+/// Wegpunkten loest daher keinen erneuten Kachel-Download aus.
+class TerrainNotifier extends Notifier<TerrainState> {
+  @override
+  TerrainState build() => const TerrainState();
+
+  Future<void> ensureFor(List<Waypoint> waypoints) async {
+    if (waypoints.length < 2) {
+      if (state.profile != null) state = const TerrainState();
+      return;
+    }
+    final routeKey = routeKeyForTerrain(waypoints);
+    if (state.profile?.routeKey == routeKey) return;
+    if (state.loading) return;
+
+    state = state.copyWith(loading: true);
+    final profile = await ref.read(terrainServiceProvider).fetchProfile(waypoints);
+    // Waehrenddessen koennte sich die Route erneut geaendert haben - nur
+    // uebernehmen, wenn das Ergebnis noch zur aktuell angefragten Route passt.
+    if (profile != null && profile.routeKey != routeKeyForTerrain(waypoints)) {
+      state = state.copyWith(loading: false);
+      return;
+    }
+    state = TerrainState(profile: profile ?? state.profile, loading: false);
+  }
+}
+
+final terrainProvider = NotifierProvider<TerrainNotifier, TerrainState>(TerrainNotifier.new);

app/lib/ui/widgets/full_value_chart.dart

@@ -3,16 +3,13 @@ import 'dart:math' as math;
 import 'package:flutter/material.dart';
 import 'package:latlong2/latlong.dart' hide Path;
 
+import '../../domain/mission/terrain_math.dart';
 import '../../domain/waypoint/flat_waypoint_list.dart';
 
 /// Vollbild-Chart zum Anpassen von Hoehe/Geschwindigkeit per Drag auf den
 /// Punkten (HTML-Demonstrator: buildFullChart()/attachChartDrag()). Jeder
 /// Punkt entspricht einem Wegpunkt, X-Position proportional zur
 /// zurueckgelegten Distanz entlang der Route.
-///
-/// Terrain-Overlay und Wind-Diamanten aus dem Demonstrator sind nicht
-/// portiert, da Terrain- (Doku 3.9) und Wind-System (Doku 3.8) in der
-/// Flutter-App noch nicht existieren.
 class FullValueChart extends StatefulWidget {
   const FullValueChart({
     super.key,
@@ -29,6 +26,9 @@ class FullValueChart extends StatefulWidget {
     required this.onChanged,
     this.legWind,
     this.groundSpeeds,
+    this.terrainPoints,
+    this.terrainDangerRanges,
+    this.terrainLoading = false,
   });
 
   final List<Waypoint> waypoints;
@@ -51,6 +51,17 @@ class FullValueChart extends StatefulWidget {
   /// Laenge/Null-Semantik wie [legWind].
   final List<double?>? groundSpeeds;
 
+  /// Gelaendeprofil entlang der Route (nur Altitude-Tab, Doku 3.9), relativ
+  /// zum ersten gueltigen Sample - null, solange noch nicht geladen.
+  final List<TerrainSamplePoint>? terrainPoints;
+
+  /// Streckenabschnitte mit zu geringem Bodenabstand (Doku 3.9), als
+  /// [start, end]-Distanzpaare.
+  final List<(double, double)>? terrainDangerRanges;
+
+  /// Zeigt einen dezenten Hinweis, solange das Gelaendeprofil noch laedt.
+  final bool terrainLoading;
+
   static const _distance = Distance(roundResult: false);
 
   static List<double> cumulativeDistances(List<Waypoint> waypoints) {
@@ -80,6 +91,8 @@ class _FullValueChartState extends State<FullValueChart> {
       ...widget.values,
       for (final v in widget.legWind ?? const <double?>[]) ?v,
       for (final v in widget.groundSpeeds ?? const <double?>[]) ?v,
+      for (final p in widget.terrainPoints ?? const <TerrainSamplePoint>[])
+        ?p.elevationRelM,
     ];
     if (allVals.isEmpty) return (lo: widget.min, hi: widget.max);
     final dataMin = allVals.reduce(math.min);
@@ -160,7 +173,9 @@ class _FullValueChartState extends State<FullValueChart> {
           },
           onPanEnd: (_) => _dragIndex = null,
           onPanCancel: () => _dragIndex = null,
-          child: CustomPaint(
+          child: Stack(
+            children: [
+              CustomPaint(
                 size: size,
                 painter: _ChartPainter(
                   waypoints: widget.waypoints,
@@ -174,8 +189,21 @@ class _FullValueChartState extends State<FullValueChart> {
                   unit: widget.unit,
                   legWind: widget.legWind,
                   groundSpeeds: widget.groundSpeeds,
+                  terrainPoints: widget.terrainPoints,
+                  terrainDangerRanges: widget.terrainDangerRanges,
                 ),
               ),
+              if (widget.terrainLoading && widget.terrainPoints == null)
+                const Positioned(
+                  left: 50,
+                  bottom: 4,
+                  child: Text(
+                    'Loading terrain…',
+                    style: TextStyle(color: Colors.white38, fontSize: 10),
+                  ),
+                ),
+            ],
+          ),
         );
       },
     );
@@ -195,6 +223,8 @@ class _ChartPainter extends CustomPainter {
     required this.unit,
     this.legWind,
     this.groundSpeeds,
+    this.terrainPoints,
+    this.terrainDangerRanges,
   });
 
   final List<Waypoint> waypoints;
@@ -208,6 +238,8 @@ class _ChartPainter extends CustomPainter {
   final String unit;
   final List<double?>? legWind;
   final List<double?>? groundSpeeds;
+  final List<TerrainSamplePoint>? terrainPoints;
+  final List<(double, double)>? terrainDangerRanges;
 
   static const _padX = 50.0;
   static const _padY = 20.0;
@@ -219,6 +251,11 @@ class _ChartPainter extends CustomPainter {
     return _padX + (cumDist[idx] / total) * (boxW - 2 * _padX);
   }
 
+  double _xAtDist(double distanceM, double boxW) {
+    final total = cumDist.isEmpty || cumDist.last == 0 ? 1.0 : cumDist.last;
+    return _padX + (distanceM / total) * (boxW - 2 * _padX);
+  }
+
   double _yAt(double val, double boxH) =>
       boxH - _padY - ((val - lo) / (hi - lo)) * (boxH - 2 * _padY);
 
@@ -239,6 +276,10 @@ class _ChartPainter extends CustomPainter {
     final boxH = size.height;
     final n = waypoints.length;
 
+    // Gefahrenzonen zuunterst, damit Gitter/Gelaende/Kurve gut lesbar
+    // darueber liegen (HTML-Demonstrator: dangerHtml vor grid).
+    _paintDangerBands(canvas, boxW, boxH);
+
     // Gridlines mit gerundeten Werten.
     final step = _niceStep(hi - lo, 5);
     final gridPaint = Paint()
@@ -262,6 +303,7 @@ class _ChartPainter extends CustomPainter {
       v += step;
     }
 
+    _paintTerrain(canvas, boxW, boxH);
     _paintWindAndGroundSpeed(canvas, boxW, boxH);
 
     // Verbindungslinien (rot bei nicht fliegbarer Steig-/Sinkrate).
@@ -295,6 +337,46 @@ class _ChartPainter extends CustomPainter {
     }
   }
 
+  /// Rote Bereiche mit zu geringem Bodenabstand (nur Altitude-Tab, Doku
+  /// 3.9/3.10) - analog dangerHtml im HTML-Demonstrator, ganz zuunterst
+  /// gezeichnet.
+  void _paintDangerBands(Canvas canvas, double boxW, double boxH) {
+    final ranges = terrainDangerRanges;
+    if (ranges == null || ranges.isEmpty) return;
+    final paint = Paint()..color = const Color(0xFFE2574A).withValues(alpha: 0.22);
+    for (final (start, end) in ranges) {
+      final x0 = _xAtDist(start, boxW);
+      final x1 = _xAtDist(end, boxW);
+      canvas.drawRect(Rect.fromLTWH(x0, 0, math.max(x1 - x0, 2), boxH), paint);
+    }
+  }
+
+  /// Braune Gelaende-Flaeche unter dem Hoehenprofil (nur Altitude-Tab, Doku
+  /// 3.9) - analog terrainHtml im HTML-Demonstrator, direkt nach dem
+  /// Gitter und vor Wind/Soll-Kurve gezeichnet.
+  void _paintTerrain(Canvas canvas, double boxW, double boxH) {
+    final points = terrainPoints;
+    if (points == null) return;
+    final valid = points.where((p) => p.elevationRelM != null).toList();
+    if (valid.length < 2) return;
+
+    final path = Path()..moveTo(_xAtDist(valid.first.distanceM, boxW), boxH - _padY);
+    for (final p in valid) {
+      path.lineTo(_xAtDist(p.distanceM, boxW), _yAt(p.elevationRelM!, boxH));
+    }
+    path.lineTo(_xAtDist(valid.last.distanceM, boxW), boxH - _padY);
+    path.close();
+
+    canvas.drawPath(path, Paint()..color = const Color(0xFF786450).withValues(alpha: 0.45));
+    canvas.drawPath(
+      path,
+      Paint()
+        ..color = const Color(0xFFAA9678).withValues(alpha: 0.8)
+        ..style = PaintingStyle.stroke
+        ..strokeWidth = 1.5,
+    );
+  }
+
   /// Wind-Diamanten je Leg (Kopf-/Rueckenwind-Komponente) und die daraus
   /// erreichbare Bodengeschwindigkeit als gestrichelte Stufenlinie - nur auf
   /// dem Speed-Tab genutzt (Doku 3.8, windHtml/groundSpeedHtml im HTML-
@@ -426,5 +508,7 @@ class _ChartPainter extends CustomPainter {
       oldDelegate.lo != lo ||
       oldDelegate.hi != hi ||
       oldDelegate.legWind != legWind ||
-      oldDelegate.groundSpeeds != groundSpeeds;
+      oldDelegate.groundSpeeds != groundSpeeds ||
+      oldDelegate.terrainPoints != terrainPoints ||
+      oldDelegate.terrainDangerRanges != terrainDangerRanges;
 }

app/lib/ui/widgets/waypoint_list_panel.dart

@@ -4,10 +4,12 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../domain/mission/default_drone_profile.dart';
 import '../../domain/mission/drone_profile.dart';
 import '../../domain/mission/route_geometry.dart';
+import '../../domain/mission/terrain_math.dart';
 import '../../domain/waypoint/flat_waypoint_list.dart';
 import '../../domain/wind/wind_math.dart';
 import '../providers/active_drone_profile_provider.dart';
 import '../providers/current_mission_provider.dart';
+import '../providers/terrain_provider.dart';
 import '../providers/wind_provider.dart';
 import 'full_value_chart.dart';
 import 'waypoint_chip.dart';
@@ -74,6 +76,16 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
   void initState() {
     super.initState();
     WidgetsBinding.instance.addPostFrameCallback((_) => _scrollToActive());
+    // Laedt/aktualisiert das Gelaendeprofil (Doku 3.9) nur, waehrend der
+    // Altitude-Tab tatsaechlich sichtbar ist - aendert sich die Route
+    // waehrenddessen (Editieren, Loeschen, neuer Wegpunkt), muss neu
+    // gesampelt werden. ensureFor() selbst filtert per routeKey, ob ein
+    // erneuter Kachel-Download noetig ist.
+    ref.listenManual(currentMissionProvider, (previous, next) {
+      if (_tab == _PanelTab.altitude) {
+        ref.read(terrainProvider.notifier).ensureFor(next);
+      }
+    });
   }
 
   @override
@@ -137,6 +149,7 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
   Widget build(BuildContext context) {
     final waypoints = ref.watch(currentMissionProvider);
     final droneProfile = ref.watch(activeDroneProfileProvider);
+    final terrainState = ref.watch(terrainProvider);
     final routeGeometry = buildRouteGeometry(
       waypoints,
       minTurnRadius: droneProfile.minTurnRadius,
@@ -204,6 +217,11 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
                     pxPerUnit: 5,
                     unit: ' m',
                     onChanged: widget.onAltitudeChanged,
+                    terrainPoints: terrainState.profile?.points,
+                    terrainDangerRanges: terrainState.profile != null
+                        ? terrainDangerRanges(waypoints, terrainState.profile!)
+                        : null,
+                    terrainLoading: terrainState.loading,
                   ),
                 _PanelTab.speed => _chartTab(
                     waypoints,
@@ -234,6 +252,8 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
           setState(() => _tab = tab);
           if (tab == _PanelTab.list) {
             WidgetsBinding.instance.addPostFrameCallback((_) => _scrollToActive());
+          } else if (tab == _PanelTab.altitude) {
+            ref.read(terrainProvider.notifier).ensureFor(ref.read(currentMissionProvider));
           }
         },
         child: Container(
@@ -272,6 +292,9 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
     required void Function(int index, double value) onChanged,
     List<double?>? legWind,
     List<double?>? groundSpeeds,
+    List<TerrainSamplePoint>? terrainPoints,
+    List<(double, double)>? terrainDangerRanges,
+    bool terrainLoading = false,
   }) {
     return Padding(
       padding: const EdgeInsets.fromLTRB(8, 16, 8, 8),
@@ -289,6 +312,9 @@ class _WaypointListPanelState extends ConsumerState<WaypointListPanel> {
         onChanged: onChanged,
         legWind: legWind,
         groundSpeeds: groundSpeeds,
+        terrainPoints: terrainPoints,
+        terrainDangerRanges: terrainDangerRanges,
+        terrainLoading: terrainLoading,
       ),
     );
   }

app/test/domain/terrain_math_test.dart

@@ -0,0 +1,151 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:dmc_app/domain/mission/terrain_math.dart';
+import 'package:dmc_app/domain/waypoint/flat_waypoint_list.dart';
+
+void main() {
+  group('routeKeyForTerrain', () {
+    test('aendert sich, wenn sich ein Wegpunkt verschiebt', () {
+      const a = [
+        Waypoint(lat: 52.0, lon: 4.0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+      const b = [
+        Waypoint(lat: 52.001, lon: 4.0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+
+      expect(routeKeyForTerrain(a), isNot(routeKeyForTerrain(b)));
+    });
+
+    test('bleibt gleich bei reinen Wertaenderungen (Hoehe/Geschwindigkeit)', () {
+      const a = [
+        Waypoint(lat: 52.0, lon: 4.0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+      const b = [
+        Waypoint(lat: 52.0, lon: 4.0, altitudeM: 120, speedMs: 20, catchRadiusM: 60),
+      ];
+
+      expect(routeKeyForTerrain(a), routeKeyForTerrain(b));
+    });
+  });
+
+  group('sampleCountFor', () {
+    test('klemmt sehr kurze Routen auf mindestens 10 Samples', () {
+      const waypoints = [
+        Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+        Waypoint(lat: 0.0001, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+      expect(sampleCountFor(waypoints), 10);
+    });
+
+    test('folgt der 30-m-Sampling-Distanz fuer laengere Routen', () {
+      // 1 Grad Breite ~ 111.320 km -> 0.01 Grad ~ 1113 m.
+      const waypoints = [
+        Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+        Waypoint(lat: 0.01, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+      final count = sampleCountFor(waypoints);
+      expect(count, greaterThan(10));
+      expect(count, closeTo(1113 / terrainSampleSpacingM, 2));
+    });
+
+    test('liefert 0 fuer eine einzelne Wegpunkt-Route', () {
+      const waypoints = [
+        Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      ];
+      expect(sampleCountFor(waypoints), 0);
+    });
+  });
+
+  group('sampleRouteByDistance', () {
+    const waypoints = [
+      Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      Waypoint(lat: 0, lon: 0.01, altitudeM: 80, speedMs: 15, catchRadiusM: 60),
+    ];
+
+    test('erstes und letztes Sample entsprechen den Wegpunkten', () {
+      final samples = sampleRouteByDistance(waypoints, 10);
+
+      expect(samples, hasLength(11));
+      expect(samples.first.distanceM, 0);
+      expect(samples.first.point.latitude, closeTo(0, 1e-9));
+      expect(samples.first.point.longitude, closeTo(0, 1e-9));
+      expect(samples.last.point.longitude, closeTo(0.01, 1e-9));
+    });
+
+    test('Samples sind gleichmaessig nach Distanz verteilt', () {
+      final samples = sampleRouteByDistance(waypoints, 4);
+      final total = samples.last.distanceM;
+
+      for (var i = 0; i < samples.length; i++) {
+        expect(samples[i].distanceM, closeTo(total * i / 4, 1e-6));
+      }
+    });
+  });
+
+  group('plannedAltitudeAt', () {
+    const waypoints = [
+      Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      Waypoint(lat: 0, lon: 0.01, altitudeM: 120, speedMs: 15, catchRadiusM: 60),
+    ];
+
+    test('interpoliert linear zwischen zwei Wegpunkten', () {
+      final total = sampleRouteByDistance(waypoints, 1).last.distanceM;
+      expect(plannedAltitudeAt(waypoints, total / 2), closeTo(90, 0.5));
+    });
+
+    test('klemmt vor dem ersten und nach dem letzten Wegpunkt', () {
+      expect(plannedAltitudeAt(waypoints, -100), 60);
+      final total = sampleRouteByDistance(waypoints, 1).last.distanceM;
+      expect(plannedAltitudeAt(waypoints, total + 1000), 120);
+    });
+  });
+
+  group('terrainDangerRanges', () {
+    const waypoints = [
+      Waypoint(lat: 0, lon: 0, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+      Waypoint(lat: 0, lon: 0.01, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+    ];
+
+    test('meldet keinen gefaehrlichen Bereich bei ausreichendem Abstand', () {
+      final profile = TerrainProfile(routeKey: 'k', points: const [
+        TerrainSamplePoint(distanceM: 0, elevationRelM: 0),
+        TerrainSamplePoint(distanceM: 500, elevationRelM: 0),
+        TerrainSamplePoint(distanceM: 1000, elevationRelM: 0),
+      ]);
+
+      expect(terrainDangerRanges(waypoints, profile), isEmpty);
+    });
+
+    test('markiert den Bereich, in dem der Bodenabstand unterschritten wird', () {
+      // Geplante Hoehe konstant 60m; Clearance = 60 - elevRel.
+      final profile = TerrainProfile(routeKey: 'k', points: const [
+        TerrainSamplePoint(distanceM: 0, elevationRelM: 0), // clearance 60
+        TerrainSamplePoint(distanceM: 300, elevationRelM: 55), // clearance 5 (< 10)
+        TerrainSamplePoint(distanceM: 600, elevationRelM: 52), // clearance 8 (< 10)
+        TerrainSamplePoint(distanceM: 900, elevationRelM: 0), // clearance 60
+      ]);
+
+      final ranges = terrainDangerRanges(waypoints, profile);
+
+      expect(ranges, [(300.0, 900.0)]);
+    });
+
+    test('ignoriert Samples ohne geladene Hoehe', () {
+      final profile = TerrainProfile(routeKey: 'k', points: const [
+        TerrainSamplePoint(distanceM: 0, elevationRelM: null),
+        TerrainSamplePoint(distanceM: 500),
+      ]);
+
+      expect(terrainDangerRanges(waypoints, profile), isEmpty);
+    });
+
+    test('schliesst einen bis zum letzten Sample andauernden Bereich ab', () {
+      final profile = TerrainProfile(routeKey: 'k', points: const [
+        TerrainSamplePoint(distanceM: 0, elevationRelM: 55), // clearance 5
+        TerrainSamplePoint(distanceM: 500, elevationRelM: 55),
+      ]);
+
+      expect(terrainDangerRanges(waypoints, profile), [(0.0, 500.0)]);
+    });
+  });
+}

app/test/services/terrain_service_test.dart

@@ -0,0 +1,78 @@
+import 'dart:async';
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+
+import 'package:dmc_app/domain/waypoint/flat_waypoint_list.dart';
+import 'package:dmc_app/services/terrain/terrain_service.dart';
+
+/// Baut eine 256x256-PNG, deren Pixel alle dieselbe Terrarium-kodierte
+/// Hoehe tragen - reicht aus, um die komplette Pipeline (HTTP-Fetch,
+/// PNG-Decodierung, Terrarium-Formel, Relativierung) zu pruefen, ohne dass
+/// die exakte Pixelposition innerhalb der Kachel eine Rolle spielt.
+Future<Uint8List> _uniformElevationPng(int r, int g, int b) async {
+  const size = 256;
+  final pixels = Uint8List(size * size * 4);
+  for (var i = 0; i < size * size; i++) {
+    pixels[i * 4] = r;
+    pixels[i * 4 + 1] = g;
+    pixels[i * 4 + 2] = b;
+    pixels[i * 4 + 3] = 255;
+  }
+  final completer = Completer<ui.Image>();
+  ui.decodeImageFromPixels(
+    pixels,
+    size,
+    size,
+    ui.PixelFormat.rgba8888,
+    completer.complete,
+  );
+  final image = await completer.future;
+  final byteData = await image.toByteData(format: ui.ImageByteFormat.png);
+  return byteData!.buffer.asUint8List();
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  const waypoints = [
+    Waypoint(lat: 48.1351, lon: 11.5820, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+    Waypoint(lat: 48.1360, lon: 11.5830, altitudeM: 60, speedMs: 15, catchRadiusM: 60),
+  ];
+
+  test('fetchProfile decodiert die Terrarium-PNG in relative Hoehen', () async {
+    // R=128, G=100, B=0 -> (128*256 + 100 + 0/256) - 32768 = 100.
+    final pngBytes = await _uniformElevationPng(128, 100, 0);
+    final client = MockClient((request) async => http.Response.bytes(pngBytes, 200));
+    final service = TerrainService(client: client);
+
+    final profile = await service.fetchProfile(waypoints);
+
+    expect(profile, isNotNull);
+    expect(profile!.points, isNotEmpty);
+    // Gleichfoermiges Gelaende: jedes Sample hat dieselbe absolute Hoehe
+    // wie das erste gueltige -> relative Hoehe ueberall 0.
+    for (final p in profile.points) {
+      expect(p.elevationRelM, isNotNull);
+      expect(p.elevationRelM, closeTo(0, 0.01));
+    }
+    expect(profile.points.first.distanceM, 0);
+  });
+
+  test('fetchProfile liefert null, wenn keine Kachel geladen werden kann', () async {
+    final client = MockClient((request) async => http.Response('', 500));
+    final service = TerrainService(client: client);
+
+    expect(await service.fetchProfile(waypoints), isNull);
+  });
+
+  test('fetchProfile liefert null fuer eine einzelne Wegpunkt-Route', () async {
+    final client = MockClient((request) async => http.Response('', 500));
+    final service = TerrainService(client: client);
+
+    expect(await service.fetchProfile([waypoints.first]), isNull);
+  });
+}