fix(stats): reject sub-threshold gps drift

docs/ops/2026-07-20-daily-mileage-track-reconciliation.md

@@ -22,6 +22,7 @@ stat-writer 已支持在累计里程缺失时，用有速度证据的相邻 GPS
 - 重复累计里程仍保留为 `skipped_same_mileage` 证据；
 - GB32960、宇通只有在设备速度大于 0 且坐标有效时才进入 GPS 累计；
 - GPS 状态仍按 10 秒节流，并拒绝超过 10 分钟、时间倒序或隐含速度超过 220 km/h 的线段；
+- 低于 100 米的累计仅保留为内部状态，不生成业务日里程候选；
 - 正向仪表累计里程优先于 GPS 估算，真实仪表值恢复后会自动覆盖估算；
 - 静止车辆不会因 GPS 漂移产生虚假里程。
 

docs/ops/vehicle-ingest-runbook.md

@@ -511,7 +511,7 @@ BACKFILL_DATE_TO=2026-07-12 \
 
 宇通协议会把定位、车况和仪表里程拆成不同的稀疏帧。当天只有明确 `meter_speed=0` 的定位帧、但没有新的仪表总里程帧时，stat-writer 会用同一来源最近的历史总里程生成一条显式 `0 km` 记录，`quality_reason=stationary_carry_forward`；后续收到真实总里程后仍会正常覆盖增长。`vehicle_stat_samples_total{status="recovered_stationary"}` 用于观察该恢复路径。历史补录只能在轨迹核验确认为 `0 km` 后，临时为单次 `stats-backfill` 增加 `BACKFILL_STATIONARY_CARRY_FORWARD=true`；该开关默认关闭，禁止写入 timer，避免仅凭最新静止状态推断整日未行驶。
 
-三类协议都优先采用终端上报的累计里程字段。部分终端只有坐标、速度而累计里程稀疏或停止刷新时，stat-writer 会按同一 VIN、自然日、协议和物理来源累计相邻坐标距离，状态持久化在 `vehicle_daily_gps_mileage_state`，并以 `quality_reason=gps_coordinate_accumulation` 写入低优先级候选。该路径既覆盖总里程字段缺失，也覆盖字段存在但数值与上一帧相同；重复总里程仍计入 `skipped_same_mileage` 证据，只有同时具备有效移动点时才增加 GPS 候选。JT808 兼容没有速度字段的存量终端；GB32960、宇通 MQTT 必须同时满足设备速度大于 0，且实时状态写入按 10 秒节流，避免静止 GPS 漂移和 1 秒级宇通上报放大 MySQL 压力。相邻点超过 10 分钟、时间倒序或隐含速度超过 220 km/h 的线段不累计。选举顺序为“正向累计里程 > 正向 GPS 轨迹估算 > 累计里程零值占位”，因此稀疏累计里程造成的错误 0 km 会被已有移动轨迹纠正，真实正向累计里程恢复后仍会自动覆盖估算值；禁止把估算值混入平台累计里程归并。`vehicle_stat_samples_total{status="recovered_gps_coordinate"}` 和 `vehicle_stat_cache_entries{cache="gps_accumulation"}` 用于观察实时恢复量及节流缓存。`stats-backfill` 默认用 TDengine `vehicle_locations` 为缺少正向累计里程但存在可用移动线段的车辆补建同口径候选；可临时设置 `BACKFILL_GPS_FALLBACK=false` 禁用全部协议的降级路径，旧环境变量 `BACKFILL_JT808_GPS_FALLBACK` 继续兼容。
+三类协议都优先采用终端上报的累计里程字段。部分终端只有坐标、速度而累计里程稀疏或停止刷新时，stat-writer 会按同一 VIN、自然日、协议和物理来源累计相邻坐标距离，状态持久化在 `vehicle_daily_gps_mileage_state`，并以 `quality_reason=gps_coordinate_accumulation` 写入低优先级候选。该路径既覆盖总里程字段缺失，也覆盖字段存在但数值与上一帧相同；重复总里程仍计入 `skipped_same_mileage` 证据，只有同时具备有效移动点时才增加 GPS 候选。JT808 兼容没有速度字段的存量终端；GB32960、宇通 MQTT 必须同时满足设备速度大于 0，且实时状态写入按 10 秒节流，避免静止 GPS 漂移和 1 秒级宇通上报放大 MySQL 压力。相邻点超过 10 分钟、时间倒序或隐含速度超过 220 km/h 的线段不累计；低于 100 米的自然日累计只保留在状态表中，不投影为业务候选，避免瞬时车速噪声和微小定位漂移生成虚假日里程。选举顺序为“正向累计里程 > 正向 GPS 轨迹估算 > 累计里程零值占位”，因此稀疏累计里程造成的错误 0 km 会被已有移动轨迹纠正，真实正向累计里程恢复后仍会自动覆盖估算值；禁止把估算值混入平台累计里程归并。`vehicle_stat_samples_total{status="recovered_gps_coordinate"}` 和 `vehicle_stat_cache_entries{cache="gps_accumulation"}` 用于观察实时恢复量及节流缓存。`stats-backfill` 默认用 TDengine `vehicle_locations` 为缺少正向累计里程但存在可用移动线段的车辆补建同口径候选；可临时设置 `BACKFILL_GPS_FALLBACK=false` 禁用全部协议的降级路径，旧环境变量 `BACKFILL_JT808_GPS_FALLBACK` 继续兼容。
 
 生产定时补算使用 systemd timer，默认每天 01:30 补算昨天往前 3 天，覆盖上游晚到或断传后恢复的总里程字段：
 

go/vehicle-gateway/cmd/stats-backfill/main.go

@@ -622,7 +622,7 @@ ORDER BY ts ASC`, ident(cfg.TDengineDatabase), strings.Join(where, " AND "))
 	}
 	added := 0
 	for target, state := range states {
-		if state.usableSegments == 0 {
+		if !stats.GPSMileageCandidateEligible(state.distanceKM, state.usableSegments) {
 			continue
 		}
 		parts := strings.SplitN(target, "|", 2)

go/vehicle-gateway/internal/stats/daily_metric_test.go

@@ -2128,7 +2128,7 @@ func TestWriterDuplicateYutongOdometerStillEntersGPSFallback(t *testing.T) {
 		EventTimeMS:    eventTime.UnixMilli(),
 		Fields: map[string]any{
 			"yutong_mqtt.data.total_mileage": 24245000,
-			"yutong_mqtt.data.longitude":     114.435672,
+			"yutong_mqtt.data.longitude":     114.436672,
 			"yutong_mqtt.data.latitude":      30.645438,
 			"yutong_mqtt.data.meter_speed":   18,
 		},

go/vehicle-gateway/internal/stats/gps_mileage.go

@@ -17,6 +17,7 @@ const (
 	gpsCoordinateSourceSuffix  = "#GPS_COORDINATE"
 	gpsMaxSegmentGap           = 10 * time.Minute
 	gpsMaxImpliedSpeedKMH      = 220.0
+	gpsMinimumDailyDistanceKM  = 0.1
 )
 
 const GPSMileageStateTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_gps_mileage_state (
@@ -238,7 +239,7 @@ func AccumulateGPSMileage(ctx context.Context, exec Execer, point GPSMileagePoin
 		_ = tx.Rollback()
 		return GPSMileageState{}, false, err
 	}
-	if state.UsableSegmentCount == 0 {
+	if !GPSMileageCandidateEligible(state.DailyMileageKM, state.UsableSegmentCount) {
 		if err := tx.Commit(); err != nil {
 			return GPSMileageState{}, false, err
 		}
@@ -258,6 +259,16 @@ func AccumulateGPSMileage(ctx context.Context, exec Execer, point GPSMileagePoin
 	return state, true, nil
 }
 
+// GPSMileageCandidateEligible keeps sub-100-metre stationary drift and
+// momentary speed noise in the durable accumulation state without exposing it
+// as a business daily-mileage candidate. Real movement continues accumulating
+// and becomes eligible once the evidence crosses the minimum distance.
+func GPSMileageCandidateEligible(distanceKM float64, usableSegmentCount int64) bool {
+	return usableSegmentCount > 0 &&
+		isFiniteNonNegative(distanceKM) &&
+		distanceKM >= gpsMinimumDailyDistanceKM
+}
+
 // AccumulateJT808GPSMileage remains as a compatibility wrapper for callers and
 // operational tooling compiled against the original JT808-only fallback.
 func AccumulateJT808GPSMileage(ctx context.Context, exec Execer, point GPSMileagePoint) (GPSMileageState, bool, error) {

go/vehicle-gateway/internal/stats/gps_mileage_test.go

@@ -151,6 +151,18 @@ func TestWriterThrottlesHighFrequencyGPSMileageStateWrites(t *testing.T) {
 	}
 }
 
+func TestGPSMileageCandidateEligibleRejectsStationaryDrift(t *testing.T) {
+	if GPSMileageCandidateEligible(0.099999, 10) {
+		t.Fatal("sub-100-metre GPS drift must not become a daily-mileage candidate")
+	}
+	if GPSMileageCandidateEligible(0.2, 0) {
+		t.Fatal("distance without a usable segment must not become a candidate")
+	}
+	if !GPSMileageCandidateEligible(0.1, 1) {
+		t.Fatal("100 metres with a usable segment should become eligible")
+	}
+}
+
 func TestAccumulateJT808GPSMileagePersistsEstimateAndProjects(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	if err != nil {
@@ -250,3 +262,47 @@ func TestAccumulateJT808GPSMileageNeedsUsableSegmentBeforeProjection(t *testing.
 		t.Fatalf("unmet SQL expectations: %v", err)
 	}
 }
+
+func TestAccumulateGPSMileageKeepsSubThresholdDistanceAsStateOnly(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New() error = %v", err)
+	}
+	defer db.Close()
+
+	start := time.Date(2026, 7, 20, 0, 14, 56, 0, time.FixedZone("Asia/Shanghai", 8*3600))
+	point := GPSMileagePoint{
+		VIN:       "LMRKH9ACXR1004130",
+		StatDate:  "2026-07-20",
+		Protocol:  envelope.ProtocolYutongMQTT,
+		SourceKey: "YUTONG_MQTT:LMRKH9ACXR1004130@PLATFORM:yutong",
+		SourceIP:  "mqtt",
+		EventID:   "evt-small-movement",
+		EventTime: start.Add(time.Second),
+		Longitude: 114.435573,
+		Latitude:  30.645503,
+	}
+
+	mock.ExpectBegin()
+	mock.ExpectQuery("SELECT first_event_time, latest_event_time").
+		WillReturnRows(sqlmock.NewRows([]string{
+			"first_event_time", "latest_event_time", "latest_event_id",
+			"latest_longitude", "latest_latitude", "daily_mileage_km",
+			"point_count", "usable_segment_count", "bad_jump_count",
+			"long_gap_count", "out_of_order_count",
+		}).AddRow(start, start, "evt-before", 114.435572, 30.645503, 0, 1, 0, 0, 0, 0))
+	mock.ExpectExec("UPDATE vehicle_daily_gps_mileage_state").
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectCommit()
+
+	state, recovered, err := AccumulateGPSMileage(context.Background(), db, point)
+	if err != nil {
+		t.Fatalf("AccumulateGPSMileage() error = %v", err)
+	}
+	if recovered || state.DailyMileageKM <= 0 || state.DailyMileageKM >= gpsMinimumDailyDistanceKM {
+		t.Fatalf("sub-threshold state = %+v recovered=%v", state, recovered)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("unmet SQL expectations: %v", err)
+	}
+}