Merge pull request #14 from or4k2l/copilot/update-car-vmean-and-vstd

Calibrate car v_mean to PVS dataset: 13.9 → 9.5 m/s

Author: or4k2l

sgi/_internal/generator.py

@@ -28,11 +28,13 @@
 #   Truck diesel:    6-cyl, 800 RPM         → ~8 Hz
 #   Drone rotor:     DJI Mini series specs   → ~50 Hz
 #   Calibrated against PVS dataset (Menegazzo, 2020) — Brazil, dashboard IMU
+#   car v_mean = 9.5 m/s (34.2 km/h) — direct measurement from PVS GPS speed
+#   (PVS mean GPS speed: 34.5 km/h, n=1500 windows)
 MOTION_PARAMS = {
     #              v_mean  v_std  a_long  a_lat  vib_freq  vib_amp  heading_std  road_noise
     'human':   (   1.4,   0.30,  0.05,  0.03,    1.8,    0.08,     15.0,        0.0),
     'bicycle': (   4.5,   0.80,  0.10,  0.05,    2.5,    0.04,      8.0,        0.5),
-    'car':     (  13.9,   3.50,  0.80,  0.40,    5.0,    0.02,      5.0,        3.0),
+    'car':     (   9.5,   3.50,  0.80,  0.40,    5.0,    0.02,      5.0,        3.0),  # v_mean calibrated to PVS: 34.5 km/h mean
     'truck':   (  11.1,   1.20,  1.40,  0.25,    8.0,    0.08,      1.5,        3.0),
     'drone':   (   8.0,   1.50,  0.60,  0.60,   50.0,    0.03,     25.0,        0.0),
 }

tests/test_sgi.py

@@ -230,11 +230,30 @@ def test_car_vib_amp_realistic(self):
         assert np.std(w['a_vert']) > 0.001, \
             f"car a_vert std too low: {np.std(w['a_vert']):.4f} — road noise not modelled"
 
-    def test_truck_speed_lt_car(self):
-        """truck v_mean must be less than car — primary urban speed discriminator"""
+    def test_car_truck_speed_realistic(self):
+        """car and truck v_mean must both be realistic urban speeds (1–20 m/s)"""
         from sgi._internal.generator import MOTION_PARAMS
-        assert MOTION_PARAMS['truck'][0] < MOTION_PARAMS['car'][0], \
-            "truck v_mean should be less than car (urban: truck ~30km/h, car ~50km/h)"
+        car_vm   = MOTION_PARAMS['car'][0]
+        truck_vm = MOTION_PARAMS['truck'][0]
+        assert 1.0 < car_vm < 20.0,   f"car v_mean={car_vm} outside realistic urban range"
+        assert 1.0 < truck_vm < 20.0, f"truck v_mean={truck_vm} outside realistic urban range"
+
+    def test_car_vmean_calibrated(self):
+        """car v_mean must be calibrated to PVS dataset: 9.5 m/s (34.2 km/h)"""
+        from sgi._internal.generator import MOTION_PARAMS
+        assert MOTION_PARAMS['car'][0] == 9.5, (
+            f"car v_mean should be 9.5 m/s (PVS calibrated), got {MOTION_PARAMS['car'][0]}"
+        )
+
+    def test_car_truck_vmean_overlap(self):
+        """car and truck v_mean must be within 5 m/s — speed distributions overlap in reality"""
+        from sgi._internal.generator import MOTION_PARAMS
+        car_vm   = MOTION_PARAMS['car'][0]
+        truck_vm = MOTION_PARAMS['truck'][0]
+        assert abs(car_vm - truck_vm) < 5.0, (
+            f"car ({car_vm}) and truck ({truck_vm}) v_mean too far apart — "
+            "classifier cannot separate them by speed alone"
+        )
 
     def test_truck_vib_amp_gt_car(self):
         """truck a_vert std must exceed car (heavier vehicle, rougher vibration)"""