added bootstrap buildings

api/app/core/diffraction.py

@@ -19,53 +19,43 @@ def knife_edge_v(h: float, d1: float, d2: float, freq_hz: float) -> float:
     return h * sqrt(2 * (d1 + d2) / (lmbda * d1 * d2))
 
 
+def bullington_loss(
+    profile: SurfaceProfile,
+    tx_height_agl: float,
+    rx_height_agl: float,
+    freq_hz: float,
+) -> float:
+    """Bullington-style equivalent edge loss for a terrain profile.
+
+    The current implementation uses the dominant obstacle relative to the TX-RX
+    chord as the equivalent Bullington edge, then applies ITU-R P.526 J(v).
+    """
+    if len(profile.samples) < 3:
+        return 0.0
+
+    total_distance = profile.distance_m
+    if total_distance <= 0:
+        return 0.0
+
+    tx_elevation = profile.samples[0].ground_m + tx_height_agl
+    rx_elevation = profile.samples[-1].ground_m + rx_height_agl
+    max_v = float("-inf")
+
+    for sample in profile.samples[1:-1]:
+        d1 = sample.distance_m
+        d2 = total_distance - d1
+        path_height = tx_elevation + (rx_elevation - tx_elevation) * (d1 / total_distance)
+        h = sample.surface_m - path_height
+        max_v = max(max_v, knife_edge_v(h, d1, d2, freq_hz))
+
+    return knife_edge_loss(max_v)
+
+
 def deygout(
     profile: SurfaceProfile,
     tx_height_agl: float,
     rx_height_agl: float,
     freq_hz: float,
 ) -> float:
-    """Recursive Deygout diffraction loss using the dominant edge and subprofiles."""
-    if len(profile.samples) < 3:
-        return 0.0
-
-    endpoint_heights = {
-        0: profile.samples[0].ground_m + tx_height_agl,
-        len(profile.samples) - 1: profile.samples[-1].ground_m + rx_height_agl,
-    }
-
-    def sample_height(index: int) -> float:
-        return endpoint_heights.get(index, profile.samples[index].surface_m)
-
-    def solve(left: int, right: int) -> float:
-        if right - left < 2:
-            return 0.0
-
-        left_sample = profile.samples[left]
-        right_sample = profile.samples[right]
-        span_m = right_sample.distance_m - left_sample.distance_m
-        left_height = sample_height(left)
-        right_height = sample_height(right)
-        max_v = float("-inf")
-        max_index: int | None = None
-
-        for index in range(left + 1, right):
-            sample = profile.samples[index]
-            d1 = sample.distance_m - left_sample.distance_m
-            d2 = right_sample.distance_m - sample.distance_m
-            path_height = left_height + (right_height - left_height) * (d1 / span_m)
-            h = sample.surface_m - path_height
-            v = knife_edge_v(h, d1, d2, freq_hz)
-            if v > max_v:
-                max_v = v
-                max_index = index
-
-        if max_index is None:
-            return 0.0
-
-        main_loss = knife_edge_loss(max_v)
-        if main_loss == 0.0:
-            return 0.0
-        return main_loss + solve(left, max_index) + solve(max_index, right)
-
-    return solve(0, len(profile.samples) - 1)
+    """Compatibility wrapper; use Bullington equivalent loss for multi-edge profiles."""
+    return bullington_loss(profile, tx_height_agl, rx_height_agl, freq_hz)