added formulas

api/app/core/diffraction.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 from math import log10, sqrt
 
-from app.core.fresnel import wavelength
+from app.core.fresnel import earth_bulge, wavelength
 from app.core.surface import SurfaceProfile
 
 
@@ -24,6 +24,7 @@ def bullington_loss(
     tx_height_agl: float,
     rx_height_agl: float,
     freq_hz: float,
+    k: float = 1.333,
 ) -> float:
     """Bullington-style equivalent edge loss for a terrain profile.
 
@@ -45,17 +46,34 @@ def bullington_loss(
         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
+        h = sample.surface_m + earth_bulge(d1, d2, k) - path_height
         max_v = max(max_v, knife_edge_v(h, d1, d2, freq_hz))
 
     return knife_edge_loss(max_v)
 
 
+def bullington_equivalent_loss(
+    profile: SurfaceProfile,
+    tx_height_agl: float,
+    rx_height_agl: float,
+    freq_hz: float,
+    k: float = 1.333,
+) -> float:
+    return bullington_loss(profile, tx_height_agl, rx_height_agl, freq_hz, k=k)
+
+
 def deygout(
     profile: SurfaceProfile,
     tx_height_agl: float,
     rx_height_agl: float,
     freq_hz: float,
+    k: float = 1.333,
 ) -> float:
-    """Compatibility wrapper; use Bullington equivalent loss for multi-edge profiles."""
-    return bullington_loss(profile, tx_height_agl, rx_height_agl, freq_hz)
+    """Compatibility wrapper; this is Bullington-style, not multi-edge Deygout."""
+    return bullington_equivalent_loss(
+        profile,
+        tx_height_agl,
+        rx_height_agl,
+        freq_hz,
+        k=k,
+    )