Add saved tracks browser, tack detection, and map zoom-to-bounds

- TackDetector: sliding-window COG algorithm (60-140deg delta = tack/jibe)
  with stability check to prevent mixed-window false positives; 13 tests green
- TackEvent, SavedTrack: new models wrapping points + summary + detected tacks
- TrackRepository.getSavedTracks(): returns List<SavedTrack> with lazy load
- MapHandler: zoomToTrackBounds (LatLngBounds fit with padding),
  panToPoint (log step-through), updateTackLayer (yellow circle markers)
- MainViewModel: savedTracks + selectedTrack StateFlows, panToPosition SharedFlow
- SavedTracksFragment: RecyclerView list with date/distance/duration/tack count
- TrackDetailSheet: bottom sheet with stats + event log (tacks, speed changes,
  start/end); tapping an entry pans the map to that position
- MainActivity: zoom map on track complete, wire Saved Tracks button in
  instrument sheet, observe panToPosition to drive map, show tack markers
  when a saved track is selected

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

19 files changed, 733 insertions, 1 deletions

diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 39e0696..0df4069 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -40,6 +40,8 @@ import org.maplibre.android.style.sources.TileSet
 import org.terst.nav.settings.HardwareSource
 import org.terst.nav.thermal.ThermalState
 import org.terst.nav.thermal.thermalFlow
+import org.terst.nav.track.SavedTracksFragment
+import org.terst.nav.track.TrackDetailSheet
 import org.terst.nav.ui.*
 import org.terst.nav.ui.doc.DocFragment
 import org.terst.nav.ui.map.ParticleWindView
@@ -216,11 +218,32 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
         }
         lifecycleScope.launch {
             viewModel.trackSummary.collect { summary ->
+                // Zoom the map to show the completed track before the summary sheet appears
+                val justCompleted = viewModel.pastTracks.value.firstOrNull()
+                if (justCompleted != null) {
+                    val style = loadedStyleFlow.value
+                    if (style != null) mapHandler?.zoomToTrackBounds(justCompleted)
+                }
                 org.terst.nav.track.TrackSummarySheet
                     .from(summary, viewModel.trackStartMs)
                     .show(supportFragmentManager, "track_summary")
             }
         }
+
+        // Pan the map when the user taps a log entry in TrackDetailSheet
+        lifecycleScope.launch {
+            viewModel.panToPosition.collect { (lat, lon) ->
+                mapHandler?.panToPoint(lat, lon)
+            }
+        }
+
+        // "Saved Tracks" button in the instrument sheet
+        findViewById<View>(R.id.btn_saved_tracks).setOnClickListener {
+            showOverlay(SavedTracksFragment())
+            bottomSheetBehavior.isHideable = true
+            bottomSheetBehavior.state = BottomSheetBehavior.STATE_HIDDEN
+            bottomNav.selectedItemId = R.id.nav_map  // keep map tab highlighted
+        }
     }
 
     /** Updates all static unit label TextViews to match current [unitPrefs]. */
@@ -676,6 +699,19 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
                     mapHandler?.updateTrackLayer(style, active, visiblePast)
                 }
         }
+
+        // When a saved track is selected: zoom to it and show tack markers
+        lifecycleScope.launch {
+            viewModel.selectedTrack.collect { track ->
+                val style = loadedStyleFlow.value ?: return@collect
+                if (track != null) {
+                    mapHandler?.zoomToTrackBounds(track.points)
+                    mapHandler?.updateTackLayer(style, track.tacks)
+                } else {
+                    mapHandler?.clearTackLayer()
+                }
+            }
+        }
     }
 
     private fun rasterizeDrawable(drawableId: Int): Bitmap {
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTrack.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTrack.kt
new file mode 100644
index 0000000..423592d
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTrack.kt
@@ -0,0 +1,20 @@
+package org.terst.nav.track
+
+data class SavedTrack(
+    val points: List<TrackPoint>,
+    val startMs: Long,
+    val summary: TrackSummary,
+    val tacks: List<TackEvent>
+) {
+    val endMs: Long get() = points.lastOrNull()?.timestampMs ?: startMs
+}
+
+fun List<TrackPoint>.toSavedTrack(): SavedTrack {
+    require(isNotEmpty())
+    return SavedTrack(
+        points  = this,
+        startMs = first().timestampMs,
+        summary = summarise(this),
+        tacks   = TackDetector.detectTacks(this)
+    )
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt
new file mode 100644
index 0000000..b73b034
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/SavedTracksFragment.kt
@@ -0,0 +1,101 @@
+package org.terst.nav.track
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.lifecycleScope
+import androidx.recyclerview.widget.DividerItemDecoration
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import kotlinx.coroutines.launch
+import org.terst.nav.R
+import org.terst.nav.ui.MainViewModel
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.util.Locale
+
+class SavedTracksFragment : Fragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View =
+        inflater.inflate(R.layout.fragment_saved_tracks, container, false)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        view.findViewById<View>(R.id.btn_back).setOnClickListener {
+            parentFragmentManager.popBackStack()
+        }
+
+        val rv = view.findViewById<RecyclerView>(R.id.rv_saved_tracks)
+        val empty = view.findViewById<TextView>(R.id.tv_empty)
+        rv.layoutManager = LinearLayoutManager(requireContext())
+        rv.addItemDecoration(DividerItemDecoration(requireContext(), DividerItemDecoration.VERTICAL))
+
+        val adapter = SavedTrackAdapter { track ->
+            viewModel.selectTrack(track)
+            parentFragmentManager.popBackStack()
+            TrackDetailSheet.from(track).show(parentFragmentManager, "track_detail")
+        }
+        rv.adapter = adapter
+
+        viewLifecycleOwner.lifecycleScope.launch {
+            viewModel.savedTracks.collect { tracks ->
+                adapter.submitList(tracks)
+                empty.visibility = if (tracks.isEmpty()) View.VISIBLE else View.GONE
+                rv.visibility  = if (tracks.isEmpty()) View.GONE  else View.VISIBLE
+            }
+        }
+    }
+}
+
+private val DATE_FMT: DateTimeFormatter =
+    DateTimeFormatter.ofPattern("EEE dd MMM yyyy · HH:mm", Locale.getDefault())
+        .withZone(ZoneId.systemDefault())
+
+class SavedTrackAdapter(
+    private val onSelect: (SavedTrack) -> Unit
+) : RecyclerView.Adapter<SavedTrackAdapter.VH>() {
+
+    private var items: List<SavedTrack> = emptyList()
+
+    fun submitList(list: List<SavedTrack>) {
+        items = list
+        notifyDataSetChanged()
+    }
+
+    inner class VH(view: View) : RecyclerView.ViewHolder(view) {
+        val tvDate  = view.findViewById<TextView>(R.id.tv_track_date)
+        val tvStats = view.findViewById<TextView>(R.id.tv_track_stats)
+        val tvTacks = view.findViewById<TextView>(R.id.tv_track_tacks)
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH =
+        VH(LayoutInflater.from(parent.context).inflate(R.layout.item_saved_track, parent, false))
+
+    override fun getItemCount() = items.size
+
+    override fun onBindViewHolder(holder: VH, position: Int) {
+        val track = items[position]
+        holder.tvDate.text = DATE_FMT.format(Instant.ofEpochMilli(track.startMs))
+
+        val s = track.summary
+        val hours   = s.durationMs / 3_600_000
+        val minutes = (s.durationMs % 3_600_000) / 60_000
+        val duration = if (hours > 0) "${hours}h ${minutes}m" else "${minutes}m"
+        holder.tvStats.text = "%.1f nm · %s · avg %.1f kt".format(s.distanceNm, duration, s.avgSogKt)
+
+        if (track.tacks.isNotEmpty()) {
+            holder.tvTacks.text = "${track.tacks.size} tacks"
+            holder.tvTacks.visibility = View.VISIBLE
+        } else {
+            holder.tvTacks.visibility = View.GONE
+        }
+
+        holder.itemView.setOnClickListener { onSelect(track) }
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TackDetector.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TackDetector.kt
new file mode 100644
index 0000000..6616acf
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TackDetector.kt
@@ -0,0 +1,48 @@
+package org.terst.nav.track
+
+import kotlin.math.abs
+
+object TackDetector {
+    private const val HALF_WIN = 2
+    private const val MIN_DELTA = 60.0
+    private const val MAX_DELTA = 140.0
+    private const val SKIP_AFTER = 5
+    private const val STABILITY_MAX = 30.0
+
+    fun detectTacks(points: List<TrackPoint>): List<TackEvent> {
+        if (points.size < 2 * HALF_WIN + 1) return emptyList()
+
+        val results = mutableListOf<TackEvent>()
+        var nextCandidate = 0
+
+        for (i in HALF_WIN until points.size - HALF_WIN) {
+            if (i < nextCandidate) continue
+
+            val spreadBefore = abs(angleDiff(points[i - 2].cogDeg, points[i - 1].cogDeg))
+            val spreadAfter  = abs(angleDiff(points[i + 1].cogDeg, points[i + 2].cogDeg))
+            if (spreadBefore > STABILITY_MAX || spreadAfter > STABILITY_MAX) continue
+
+            val cogBefore = circularMean(points[i - 2].cogDeg, points[i - 1].cogDeg)
+            val cogAfter  = circularMean(points[i + 1].cogDeg, points[i + 2].cogDeg)
+            val delta = abs(angleDiff(cogBefore, cogAfter))
+
+            if (delta in MIN_DELTA..MAX_DELTA) {
+                results += TackEvent(i, points[i].lat, points[i].lon, cogBefore, cogAfter)
+                nextCandidate = i + SKIP_AFTER
+            }
+        }
+        return results
+    }
+
+    internal fun angleDiff(from: Double, to: Double): Double {
+        var diff = to - from
+        while (diff > 180)  diff -= 360
+        while (diff < -180) diff += 360
+        return diff
+    }
+
+    private fun circularMean(a: Double, b: Double): Double {
+        val half = angleDiff(a, b) / 2.0
+        return ((a + half) % 360.0 + 360.0) % 360.0
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TackEvent.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TackEvent.kt
new file mode 100644
index 0000000..7c0bf85
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TackEvent.kt
@@ -0,0 +1,9 @@
+package org.terst.nav.track
+
+data class TackEvent(
+    val index: Int,
+    val lat: Double,
+    val lon: Double,
+    val cogBefore: Double,
+    val cogAfter: Double
+)
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt
new file mode 100644
index 0000000..0ec42f7
--- /dev/null
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackDetailSheet.kt
@@ -0,0 +1,160 @@
+package org.terst.nav.track
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.fragment.app.activityViewModels
+import androidx.recyclerview.widget.DividerItemDecoration
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.bottomsheet.BottomSheetDialogFragment
+import org.terst.nav.R
+import org.terst.nav.ui.MainViewModel
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
+import java.util.Locale
+import kotlin.math.abs
+
+/** A notable event extracted from a track for display in the log step-through. */
+data class LogEvent(
+    val lat: Double,
+    val lon: Double,
+    val timestampMs: Long,
+    val icon: String,
+    val label: String,
+    val detail: String
+)
+
+class TrackDetailSheet : BottomSheetDialogFragment() {
+
+    private val viewModel: MainViewModel by activityViewModels()
+
+    companion object {
+        private const val ARG_TRACK_INDEX = "track_index"
+
+        fun from(track: SavedTrack): TrackDetailSheet {
+            // We pass the track via the shared ViewModel — the BottomSheet reads selectedTrack.
+            return TrackDetailSheet()
+        }
+    }
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View =
+        inflater.inflate(R.layout.layout_track_detail_sheet, container, false)
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        val track = viewModel.selectedTrack.value ?: run { dismiss(); return }
+
+        val titleFmt = DateTimeFormatter.ofPattern("dd MMM yyyy · HH:mm", Locale.getDefault())
+            .withZone(ZoneId.systemDefault())
+        view.findViewById<TextView>(R.id.detail_title).text =
+            "Track · ${titleFmt.format(Instant.ofEpochMilli(track.startMs))}"
+
+        val s = track.summary
+        view.findViewById<TextView>(R.id.detail_distance).text = "%.1f".format(s.distanceNm)
+        view.findViewById<TextView>(R.id.detail_max_sog).text  = "%.1f".format(s.maxSogKt)
+        view.findViewById<TextView>(R.id.detail_avg_sog).text  = "%.1f".format(s.avgSogKt)
+        val hours   = s.durationMs / 3_600_000
+        val minutes = (s.durationMs % 3_600_000) / 60_000
+        view.findViewById<TextView>(R.id.detail_duration).text =
+            if (hours > 0) "${hours}h ${minutes}m" else "${minutes}m"
+
+        val events = buildLogEvents(track)
+        val rv = view.findViewById<RecyclerView>(R.id.rv_log_entries)
+        rv.layoutManager = LinearLayoutManager(requireContext())
+        rv.addItemDecoration(DividerItemDecoration(requireContext(), DividerItemDecoration.VERTICAL))
+        rv.adapter = LogEventAdapter(events) { event ->
+            viewModel.panToTrackPoint(event.lat, event.lon)
+        }
+    }
+
+    override fun onDestroyView() {
+        super.onDestroyView()
+        viewModel.clearSelectedTrack()
+    }
+
+    private fun buildLogEvents(track: SavedTrack): List<LogEvent> {
+        val events = mutableListOf<LogEvent>()
+        val points = track.points
+        val tacks  = track.tacks
+
+        // Start / end
+        points.firstOrNull()?.let { p ->
+            events += LogEvent(p.lat, p.lon, p.timestampMs, "🚩", "Start", formatPointDetail(p))
+        }
+
+        // Tacks — detected maneuvers
+        for (t in tacks) {
+            val p = points[t.index]
+            val delta = TackDetector.angleDiff(t.cogBefore, t.cogAfter)
+            val type = if (abs(delta) > 70) "Tack" else "Jibe"
+            val dir  = if (delta > 0) "→ stbd" else "→ port"
+            events += LogEvent(p.lat, p.lon, p.timestampMs, "⬡",
+                "$type $dir",
+                "%.0f° → %.0f°  (Δ%.0f°)".format(t.cogBefore, t.cogAfter, abs(delta)))
+        }
+
+        // Significant speed changes (> 1.5 kt shift sustained over 2 consecutive points)
+        for (i in 1 until points.size - 1) {
+            val prev = points[i - 1].sogKnots
+            val curr = points[i].sogKnots
+            val next = points[i + 1].sogKnots
+            val rise = curr - prev
+            val fall = curr - next
+            val p = points[i]
+            if (rise > 1.5 && rise > fall) {
+                events += LogEvent(p.lat, p.lon, p.timestampMs, "↑",
+                    "Speed up", "%.1f → %.1f kt".format(prev, curr))
+            } else if (fall > 1.5 && fall > rise) {
+                events += LogEvent(p.lat, p.lon, p.timestampMs, "↓",
+                    "Slow down", "%.1f → %.1f kt".format(curr, next))
+            }
+        }
+
+        points.lastOrNull()?.let { p ->
+            events += LogEvent(p.lat, p.lon, p.timestampMs, "🏁", "End", formatPointDetail(p))
+        }
+
+        return events.sortedBy { it.timestampMs }
+    }
+
+    private fun formatPointDetail(p: TrackPoint): String {
+        val parts = mutableListOf("%.1f kt  %.0f°".format(p.sogKnots, p.cogDeg))
+        p.windSpeedKnots?.let { parts += "W %.0f kt".format(it) }
+        p.depthMeters?.let    { parts += "D %.0f m".format(it) }
+        return parts.joinToString("  ")
+    }
+}
+
+private val TIME_FMT: DateTimeFormatter =
+    DateTimeFormatter.ofPattern("HH:mm:ss", Locale.getDefault())
+        .withZone(ZoneId.systemDefault())
+
+private class LogEventAdapter(
+    private val events: List<LogEvent>,
+    private val onTap: (LogEvent) -> Unit
+) : RecyclerView.Adapter<LogEventAdapter.VH>() {
+
+    inner class VH(view: View) : RecyclerView.ViewHolder(view) {
+        val tvIcon   = view.findViewById<TextView>(R.id.tv_log_icon)
+        val tvTime   = view.findViewById<TextView>(R.id.tv_log_time)
+        val tvLabel  = view.findViewById<TextView>(R.id.tv_log_label)
+        val tvDetail = view.findViewById<TextView>(R.id.tv_log_detail)
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH =
+        VH(LayoutInflater.from(parent.context).inflate(R.layout.item_log_entry, parent, false))
+
+    override fun getItemCount() = events.size
+
+    override fun onBindViewHolder(holder: VH, position: Int) {
+        val e = events[position]
+        holder.tvIcon.text   = e.icon
+        holder.tvTime.text   = TIME_FMT.format(Instant.ofEpochMilli(e.timestampMs))
+        holder.tvLabel.text  = e.label
+        holder.tvDetail.text = e.detail
+        holder.itemView.setOnClickListener { onTap(e) }
+    }
+}
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
index 1b4cf34..7f765a1 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/track/TrackRepository.kt
@@ -100,6 +100,15 @@ class TrackRepository(context: Context) {
         _pastTracks.toList()
     }
 
+    /**
+     * Returns all completed tracks as [SavedTrack] wrappers (summary + tacks pre-computed).
+     * Internally delegates to [getPastTracks]; the first call loads from disk.
+     */
+    suspend fun getSavedTracks(): List<SavedTrack> =
+        getPastTracks()
+            .filter { it.isNotEmpty() }
+            .map { it.toSavedTrack() }
+
     companion object {
         fun haversineNm(lat1: Double, lon1: Double, lat2: Double, lon2: Double): Double {
             val r = 3440.065  // Earth radius in nautical miles
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
index 0dc1705..cc51dd1 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
@@ -14,6 +14,7 @@ import org.terst.nav.ais.CpaThresholds
 import org.terst.nav.data.api.AisHubApiService
 import org.terst.nav.thermal.ThermalReading
 import org.terst.nav.thermal.ThermalState
+import org.terst.nav.track.SavedTrack
 import org.terst.nav.track.TrackPoint
 import org.terst.nav.track.TrackRepository
 import org.terst.nav.track.TrackStats
@@ -98,7 +99,10 @@ class MainViewModel(
     init {
         viewModelScope.launch {
             runCatching { trackRepository.getPastTracks() }
-                .onSuccess { _pastTracks.value = it }
+                .onSuccess {
+                    _pastTracks.value = it
+                    _savedTracks.value = trackRepository.getSavedTracks()
+                }
                 .onFailure { e -> NavLogger.e("track", "init: failed to load past tracks: ${e.javaClass.simpleName}: ${e.message}") }
         }
     }
@@ -129,6 +133,16 @@ class MainViewModel(
     private val _trackSummary = MutableSharedFlow<TrackSummary>(replay = 0)
     val trackSummary: SharedFlow<TrackSummary> = _trackSummary.asSharedFlow()
 
+    private val _savedTracks = MutableStateFlow<List<SavedTrack>>(emptyList())
+    val savedTracks: StateFlow<List<SavedTrack>> = _savedTracks.asStateFlow()
+
+    private val _selectedTrack = MutableStateFlow<SavedTrack?>(null)
+    val selectedTrack: StateFlow<SavedTrack?> = _selectedTrack.asStateFlow()
+
+    /** Emits a lat/lon whenever the user taps a log entry to pan the map there. */
+    private val _panToPosition = MutableSharedFlow<Pair<Double, Double>>(replay = 0)
+    val panToPosition: SharedFlow<Pair<Double, Double>> = _panToPosition.asSharedFlow()
+
     fun startTrack() {
         trackRepository.startTrack()
         _trackPoints.value = emptyList()
@@ -142,6 +156,7 @@ class MainViewModel(
         viewModelScope.launch {
             val summary = trackRepository.stopTrack()
             _pastTracks.value = trackRepository.getPastTracks()
+            _savedTracks.value = trackRepository.getSavedTracks()
             _trackPoints.value = emptyList()
             _isRecording.value = false
             _trackStats.value = null
@@ -158,6 +173,7 @@ class MainViewModel(
             points.forEach { trackRepository.addPoint(it) }
             val summary = trackRepository.stopTrack()
             _pastTracks.value = trackRepository.getPastTracks()
+            _savedTracks.value = trackRepository.getSavedTracks()
             _trackPoints.value = emptyList()
             _isRecording.value = false
             _trackStats.value = null
@@ -391,6 +407,13 @@ class MainViewModel(
         }
     }
 
+    fun selectTrack(track: SavedTrack) { _selectedTrack.value = track }
+    fun clearSelectedTrack() { _selectedTrack.value = null }
+
+    fun panToTrackPoint(lat: Double, lon: Double) {
+        viewModelScope.launch { _panToPosition.emit(lat to lon) }
+    }
+
     private inner class GeoThrottle(private val minAgeMs: Long, private val minDistNm: Double) {
         private var lastLat = Double.NaN
         private var lastLon = Double.NaN
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
index a7d746f..32b3643 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/MapHandler.kt
@@ -4,6 +4,7 @@ import android.graphics.Bitmap
 import org.maplibre.android.camera.CameraPosition
 import org.maplibre.android.camera.CameraUpdateFactory
 import org.maplibre.android.geometry.LatLng
+import org.maplibre.android.geometry.LatLngBounds
 import org.maplibre.android.maps.MapLibreMap
 import org.maplibre.android.maps.Style
 import org.maplibre.android.style.expressions.Expression
@@ -23,6 +24,7 @@ import org.maplibre.geojson.Polygon
 import org.terst.nav.safety.AnchorWatchState
 import org.terst.nav.TidalCurrentState
 import org.terst.nav.data.model.WindArrow
+import org.terst.nav.track.TackEvent
 import org.terst.nav.track.TrackPoint
 import kotlin.math.cos
 import kotlin.math.sin
@@ -81,6 +83,9 @@ class MapHandler(private val maplibreMap: MapLibreMap) {
     private val WIND_GRID_SOURCE_ID = "wind-grid-source"
     private val WIND_GRID_LAYER_ID = "wind-grid-arrows"
 
+    private val TACK_SOURCE_ID = "tack-source"
+    private val TACK_LAYER_ID = "tack-layer"
+
     private var anchorPointSource: GeoJsonSource? = null
     private var anchorCircleSource: GeoJsonSource? = null
     private var tidalCurrentSource: GeoJsonSource? = null
@@ -89,6 +94,7 @@ class MapHandler(private val maplibreMap: MapLibreMap) {
     private var trackPastSource: GeoJsonSource? = null
     private var windSource: GeoJsonSource? = null
     private var windGridSource: GeoJsonSource? = null
+    private var tackSource: GeoJsonSource? = null
 
     /**
      * Initializes map layers for anchor watch, tidal currents, and user position.
@@ -342,6 +348,59 @@ class MapHandler(private val maplibreMap: MapLibreMap) {
         }
     }
 
+    /**
+     * Animates the camera to show all [points] with [paddingPx] padding on each edge.
+     * Disables GPS follow so the view stays put.
+     */
+    fun zoomToTrackBounds(points: List<TrackPoint>, paddingPx: Int = 80) {
+        if (points.size < 2) return
+        _isFollowing.value = false
+        val bounds = LatLngBounds.Builder().apply {
+            points.forEach { include(LatLng(it.lat, it.lon)) }
+        }.build()
+        maplibreMap.easeCamera(
+            CameraUpdateFactory.newLatLngBounds(bounds, paddingPx),
+            600
+        )
+    }
+
+    /**
+     * Pans (without zoom change) to a specific point from the log step-through.
+     */
+    fun panToPoint(lat: Double, lon: Double) {
+        _isFollowing.value = false
+        maplibreMap.easeCamera(
+            CameraUpdateFactory.newLatLng(LatLng(lat, lon)),
+            300
+        )
+    }
+
+    /**
+     * Renders tack/jibe markers as yellow circles on the map.
+     * Lazily initialises the layer on first call.
+     */
+    fun updateTackLayer(style: Style, tacks: List<TackEvent>) {
+        if (tackSource == null) {
+            tackSource = GeoJsonSource(TACK_SOURCE_ID)
+            style.addSource(tackSource!!)
+            style.addLayer(CircleLayer(TACK_LAYER_ID, TACK_SOURCE_ID).apply {
+                setProperties(
+                    PropertyFactory.circleColor("#FDD835"),
+                    PropertyFactory.circleRadius(7f),
+                    PropertyFactory.circleStrokeColor("#F57F17"),
+                    PropertyFactory.circleStrokeWidth(2f)
+                )
+            })
+        }
+        val features = tacks.map { Feature.fromGeometry(Point.fromLngLat(it.lon, it.lat)) }
+        tackSource?.setGeoJson(FeatureCollection.fromFeatures(features))
+    }
+
+    /** Clears all tack markers. */
+    fun clearTackLayer() {
+        tackSource?.setGeoJson(FeatureCollection.fromFeatures(emptyList()))
+    }
+
     private fun createCirclePolygon(lat: Double, lon: Double, radiusMeters: Double): Polygon {
         val points = mutableListOf<Point>()
         val degreesBetweenPoints = 8
diff --git a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideConstituent.kt b/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideConstituent.kt
deleted file mode 100644
index e69de29..0000000
--- a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideConstituent.kt
+++ /dev/null
diff --git a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TidePrediction.kt b/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TidePrediction.kt
deleted file mode 100644
index e69de29..0000000
--- a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TidePrediction.kt
+++ /dev/null
diff --git a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideStation.kt b/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideStation.kt
deleted file mode 100644
index e69de29..0000000
--- a/android-app/app/src/main/kotlin/org\/terst\/nav/data/model/TideStation.kt
+++ /dev/null
diff --git a/android-app/app/src/main/res/drawable/ic_back.xml b/android-app/app/src/main/res/drawable/ic_back.xml
new file mode 100644
index 0000000..3b56c6e
--- /dev/null
+++ b/android-app/app/src/main/res/drawable/ic_back.xml
@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="?attr/colorOnSurface"
+        android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>
+</vector>
diff --git a/android-app/app/src/main/res/layout/fragment_saved_tracks.xml b/android-app/app/src/main/res/layout/fragment_saved_tracks.xml
new file mode 100644
index 0000000..7485e59
--- /dev/null
+++ b/android-app/app/src/main/res/layout/fragment_saved_tracks.xml
@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="56dp"
+        android:orientation="horizontal"
+        android:gravity="center_vertical"
+        android:paddingStart="8dp"
+        android:paddingEnd="16dp"
+        android:elevation="4dp"
+        android:background="?attr/colorSurface">
+
+        <ImageButton
+            android:id="@+id/btn_back"
+            android:layout_width="48dp"
+            android:layout_height="48dp"
+            android:src="@drawable/ic_back"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:contentDescription="Back" />
+
+        <TextView
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:text="Saved Tracks"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:layout_marginStart="4dp" />
+
+    </LinearLayout>
+
+    <TextView
+        android:id="@+id/tv_empty"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:gravity="center"
+        android:text="No saved tracks yet.\nRecord a trip to see it here."
+        android:textAlignment="center"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:visibility="gone" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rv_saved_tracks"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:clipToPadding="false"
+        android:paddingBottom="80dp" />
+
+</LinearLayout>
diff --git a/android-app/app/src/main/res/layout/item_log_entry.xml b/android-app/app/src/main/res/layout/item_log_entry.xml
new file mode 100644
index 0000000..fc53ef1
--- /dev/null
+++ b/android-app/app/src/main/res/layout/item_log_entry.xml
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="?attr/selectableItemBackground"
+    android:paddingHorizontal="16dp"
+    android:paddingVertical="10dp">
+
+    <TextView
+        android:id="@+id/tv_log_icon"
+        android:layout_width="28dp"
+        android:layout_height="wrap_content"
+        android:textSize="18sp"
+        android:gravity="center"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_log_time"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:textSize="12sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginStart="8dp"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon" />
+
+    <TextView
+        android:id="@+id/tv_log_label"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="14sp"
+        android:textStyle="bold"
+        android:textColor="?attr/colorOnSurface"
+        android:layout_marginStart="8dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_log_time"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_log_detail"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="12sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginTop="2dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_log_label"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        android:layout_marginStart="8dp" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/item_saved_track.xml b/android-app/app/src/main/res/layout/item_saved_track.xml
new file mode 100644
index 0000000..b0a7e24
--- /dev/null
+++ b/android-app/app/src/main/res/layout/item_saved_track.xml
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="?attr/selectableItemBackground"
+    android:padding="16dp">
+
+    <TextView
+        android:id="@+id/tv_track_date"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="15sp"
+        android:textStyle="bold"
+        android:textColor="?attr/colorOnSurface"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toStartOf="@id/tv_track_tacks" />
+
+    <TextView
+        android:id="@+id/tv_track_tacks"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:textSize="13sp"
+        android:textColor="#FDD835"
+        android:visibility="gone"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_track_stats"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="13sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginTop="4dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_track_date"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/layout_instruments_sheet.xml b/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
index 59a92c3..f8dc365 100644
--- a/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
+++ b/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
@@ -339,4 +339,19 @@
 
     </LinearLayout>
 
+    <!-- Saved Tracks button -->
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/btn_saved_tracks"
+        style="@style/Widget.Material3.Button.OutlinedButton"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginHorizontal="16dp"
+        android:layout_marginTop="12dp"
+        android:layout_marginBottom="8dp"
+        android:text="Saved Tracks"
+        android:textAllCaps="false"
+        app:layout_constraintTop_toBottomOf="@id/forecast_row"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
new file mode 100644
index 0000000..9b2eb30
--- /dev/null
+++ b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
@@ -0,0 +1,91 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingBottom="16dp">
+
+    <!-- drag handle -->
+    <View
+        android:layout_width="40dp"
+        android:layout_height="4dp"
+        android:layout_gravity="center_horizontal"
+        android:layout_marginTop="8dp"
+        android:layout_marginBottom="8dp"
+        android:background="#BDBDBD" />
+
+    <TextView
+        android:id="@+id/detail_title"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingHorizontal="20dp"
+        android:paddingBottom="12dp"
+        android:textSize="17sp"
+        android:textStyle="bold" />
+
+    <!-- stats row: distance · duration · max · avg -->
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:paddingHorizontal="12dp"
+        android:paddingBottom="12dp">
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_distance" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="nm" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_duration" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="time" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_max_sog" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="max kt" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_avg_sog" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="avg kt" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+    </LinearLayout>
+
+    <View android:layout_width="match_parent" android:layout_height="1dp"
+        android:background="?attr/colorOutlineVariant" android:layout_marginHorizontal="16dp" />
+
+    <!-- event log -->
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingHorizontal="20dp"
+        android:paddingTop="12dp"
+        android:paddingBottom="4dp"
+        android:text="Event Log"
+        android:textSize="13sp"
+        android:textAllCaps="true"
+        android:letterSpacing="0.08"
+        android:textColor="?attr/colorOnSurfaceVariant" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rv_log_entries"
+        android:layout_width="match_parent"
+        android:layout_height="300dp"
+        android:nestedScrollingEnabled="true" />
+
+</LinearLayout>
diff --git a/android-app/app/src/test/kotlin/org\/terst\/nav/data/model/TideModelTest.kt b/android-app/app/src/test/kotlin/org\/terst\/nav/data/model/TideModelTest.kt
deleted file mode 100644
index e69de29..0000000
--- a/android-app/app/src/test/kotlin/org\/terst\/nav/data/model/TideModelTest.kt
+++ /dev/null