feat: log OBD speed before GPS fix so rolling starts aren't lost

- _log_loop: when GPS has no fix but OBD speed > 1, write speed-only rows
  (NULL coordinates) instead of dropping the motion
- insert_tracking: accept None gps_x/gps_y -> NULL GPSX/GPSY
- app_trip: keep NULL-coord rows through normalize; _segment returns 0 for
  missing coords; route_points drops them (no position to draw)
- tests: speed-only rows build a trip with max speed + zero distance
- docs: FEAT-12 + readme note; server already filters NULL-GPS safely

FEATURES.md

@@ -31,6 +31,7 @@ dedicated PLAN.md phase (or fold it into the relevant existing work) and mark it
 | FEAT-09 | `WONTFIX` | mDNS (yaris.local) on phone hotspot | — |
 | FEAT-10 | `IDEA` | Home Assistant integration | unassigned |
 | FEAT-11 | `SHIPPED` | Hotspot SSID/password settings + 5GHz WiFi role swap | Phase 27 |
+| FEAT-12 | `SHIPPED` | Log OBD speed before GPS fix (rolling-start capture) | Phase 27 |
 
 ---
 
@@ -222,3 +223,17 @@ dedicated PLAN.md phase (or fold it into the relevant existing work) and mark it
   `app_network.py` (uplink on wlan0, AP on wlan1), `install_netwatch.sh` (rebinds profiles).
 
 
+### FEAT-12 — Log OBD speed before GPS fix (rolling-start capture)
+- **Status**: `SHIPPED` 2026-08-13
+- **Area**: `modules/app_sql.py` (`_log_loop`, `insert_tracking`), `modules/app_trip.py`
+  (`normalize_tracking_rows`, `_segment`, `route_points`)
+- **What**: The tracking logger previously only wrote rows once GPS had a fix, so a rolling
+  start or mid-drive reboot lost the first ~1.5–2 min of movement (boot + GPS cold start).
+  Now, while GPS has no fix but OBD speed > 1 km/h, the logger writes speed-only rows with
+  NULL coordinates; trip building treats them as OBD-motion events (zero GPS distance). The
+  route polyline drops these rows (no position to draw).
+- **Server parity note**: server `compute_trips_for_device` and `get_trip_route` already filter
+  `gps_lat IS NOT NULL`, so they safely ignore the NULL-coordinate rows — but the server's
+  recomputed trips don't yet include the speed-only leading motion (follow-up if needed).
+
+

modules/app_sql.py

@@ -314,7 +314,11 @@ def count_active_dtcs():
 
 
 def insert_tracking(gps_x, gps_y, speed, odometer=None):
-    """Insert a single trip-tracking snapshot row (GPS position + speed)."""
+    """Insert a single trip-tracking snapshot row (GPS position + speed).
+
+    gps_x/gps_y may be None (logged before the first GPS fix) — the row then
+    stores NULL coordinates and relies on OBD speed for motion detection.
+    """
     conn = get_conn()
     if conn is None:
         return False
@@ -323,8 +327,14 @@ def insert_tracking(gps_x, gps_y, speed, odometer=None):
              VALUES (?, ?, ?, ?, ?, ?, ?)"""
     with _conn_lock:
         try:
-            latitude = float(str(gps_x).replace("\x00", "").strip())
-            longitude = float(str(gps_y).replace("\x00", "").strip())
+            latitude = (
+                None if gps_x is None
+                else float(str(gps_x).replace("\x00", "").strip())
+            )
+            longitude = (
+                None if gps_y is None
+                else float(str(gps_y).replace("\x00", "").strip())
+            )
             conn.execute(
                 sql,
                 (car.model, account.name, datetime.now(), latitude, longitude, speed, odometer),
@@ -847,6 +857,12 @@ def _log_loop():
                 ) and insert_tracking(position[0], position[1], speed, app_obd.odometer):
                     last_position = position
                     last_logged_at = now
+        elif speed is not None and speed > 1:
+            # No GPS fix yet but the car is moving (OBD speed) — log a
+            # speed-only row so a rolling start / mid-drive reboot isn't lost.
+            # Coordinates stay NULL until the first fix; trip building treats
+            # these as OBD-motion events with zero GPS distance.
+            insert_tracking(None, None, speed, app_obd.odometer)
 
         time.sleep(LOG_INTERVAL)
 

modules/app_trip.py

@@ -47,9 +47,11 @@ def normalize_tracking_rows(rows):
         longitude = _number(row[3])
         speed = _number(row[4]) or 0
         odometer = _number(row[5]) if len(row) > 5 else None
-        if timestamp is None or latitude is None or longitude is None:
+        if timestamp is None:
             continue
-        if not (-90 <= latitude <= 90 and -180 <= longitude <= 180):
+        if latitude is not None and not (-90 <= latitude <= 90):
+            continue
+        if longitude is not None and not (-180 <= longitude <= 180):
             continue
         normalized.append({
             "id": int(row[0]),
@@ -66,6 +68,11 @@ def _segment(row, previous):
     seconds = (row["datetime"] - previous["datetime"]).total_seconds()
     if seconds <= 0:
         return 0, 0
+    if (
+        previous["latitude"] is None or previous["longitude"] is None
+        or row["latitude"] is None or row["longitude"] is None
+    ):
+        return 0, 0
     distance_km = haversine_km(
         (previous["latitude"], previous["longitude"]),
         (row["latitude"], row["longitude"]),
@@ -218,6 +225,9 @@ def build_trip_summaries(raw_rows):
 
 def route_points(raw_rows, max_points=2000, odometer_baseline=0.0, prior_km=0.0):
     rows = normalize_tracking_rows(raw_rows)
+    # The route polyline needs coordinates — drop speed-only rows logged before
+    # the first GPS fix (no position to draw; they add 0 distance anyway).
+    rows = [r for r in rows if r["latitude"] is not None and r["longitude"] is not None]
     filtered_rows = []
     for row in rows:
         if filtered_rows:

readme.md

@@ -50,7 +50,8 @@ Dashboard — mobile (390 px) and desktop (1280 px):
   (create/delete/rotate keys), and server-side device identity sync that hot-reloads on the Pi.
 - **Trip history and replay** — motion-aware detection (OBD wheel speed primary, GPS displacement
   fallback). Metric summaries, offline route polyline, play/pause timeline with moving marker and
-  live reverse-geocoded location names. Tap-to-replay on mobile.
+  live reverse-geocoded location names. Tap-to-replay on mobile. Captures OBD speed before the
+  first GPS fix so rolling starts aren't lost.
 - **Status page** — Pi health (temp, RAM, disk, uptime, throttling), service states, uplink/server/
   GPS/OBD diagnostics, and quick actions (test server, sync now, reconnect uplink, restart app).
 - **Offline-first alerts** — notification bell on every page for check-engine, storage pressure,

tests/test_app_trip.py

@@ -115,6 +115,22 @@ class TripBuilderTest(unittest.TestCase):
         self.assertEqual(trips[0]["start_tracking_id"], 1)
         self.assertEqual(trips[0]["end_tracking_id"], 5)
 
+    def test_speed_only_rows_without_gps_build_trip(self):
+        started = datetime(2026, 1, 1, 8)
+        rows = [
+            (index + 1, started + timedelta(seconds=index * 5), None, None, 30)
+            for index in range(4)
+        ]
+
+        trips = app_trip.build_trip_summaries(rows)
+
+        self.assertEqual(len(trips), 1)
+        self.assertEqual(trips[0]["start_tracking_id"], 1)
+        self.assertEqual(trips[0]["end_tracking_id"], 4)
+        self.assertEqual(trips[0]["distance_km"], 0)
+        self.assertEqual(trips[0]["max_speed_kmh"], 30)
+        self.assertEqual(trips[0]["point_count"], 4)
+
     def test_clock_rollback_does_not_merge_motion_episodes(self):
         first = self.rows_for_route(
             [(45.5, -73.5), (45.5, -73.5)],