added formulas

api/app/services/link.py

@@ -47,6 +47,9 @@ def link_budget(request: LinkBudgetRequest, db: Session | None = None) -> LinkBu
     )
     atmospheric_db = atmospheric_loss_between(tx, rx, freq_hz)
 
+    active_diffraction_db = diffraction_db
+    active_atmospheric_db = atmospheric_db
+
     if request.model == "manual":
         propagation_db = 0.0
     elif request.model == "itm":
@@ -70,6 +73,7 @@ def link_budget(request: LinkBudgetRequest, db: Session | None = None) -> LinkBu
                 request.frequency_mhz,
             ).fspl_db
         )
+        active_diffraction_db = propagation_db
     elif request.model == "p452":
         propagation_db = (
             p452_loss(
@@ -91,6 +95,8 @@ def link_budget(request: LinkBudgetRequest, db: Session | None = None) -> LinkBu
                 request.frequency_mhz,
             ).fspl_db
         )
+        active_diffraction_db = propagation_db
+        active_atmospheric_db = 0.0
     else:
         raise NotImplementedError(f"{request.model} link model is not supported")
 
@@ -102,9 +108,9 @@ def link_budget(request: LinkBudgetRequest, db: Session | None = None) -> LinkBu
         rx_gain_dbi=request.rx.gain_dbi,
         sensitivity_dbm=request.rx.sensitivity_dbm,
         frequency_mhz=request.frequency_mhz,
-        diffraction_db=diffraction_db + propagation_db,
+        diffraction_db=active_diffraction_db,
         vegetation_db=vegetation_db,
-        atmospheric_db=atmospheric_db,
+        atmospheric_db=active_atmospheric_db,
         fresnel_clear=los_result.los_clear,
     )
     geometric_obstructions = [

api/tests/test_vegetation_integration.py

@@ -151,3 +151,103 @@ def test_link_viable_depends_on_margin_not_fresnel_quality(monkeypatch) -> None:
     assert result.fresnel_quality == "blocked"
     assert result.fresnel_clear is False
     assert result.link_viable is True
+
+
+def test_itm_link_budget_does_not_double_count_diffraction(monkeypatch) -> None:
+    monkeypatch.setattr(link_service, "vegetation_loss_along", lambda *args, **kwargs: 3.0)
+    monkeypatch.setattr(link_service, "atmospheric_loss_between", lambda *args, **kwargs: 2.0)
+    monkeypatch.setattr(link_service, "deygout", lambda *args, **kwargs: 99.0)
+    monkeypatch.setattr(
+        link_service,
+        "surface_profile_from_points",
+        lambda points, *args, **kwargs: SurfaceProfile(
+            distance_m=points[-1].distance_m,
+            samples=[
+                SurfaceSample(
+                    i=index,
+                    lat=point.lat,
+                    lon=point.lon,
+                    distance_m=point.distance_m,
+                    ground_m=0,
+                    building_m=0,
+                    canopy_m=0,
+                    surface_m=0,
+                )
+                for index, point in enumerate(points)
+            ],
+        ),
+    )
+
+    request = LinkBudgetRequest(
+        tx=LinkTx(lat=60.17, lon=24.94, height_agl=30, power_dbm=37, gain_dbi=8),
+        rx=LinkRx(lat=60.25, lon=25.10, height_agl=2, gain_dbi=2, sensitivity_dbm=-110),
+        frequency_mhz=433,
+        model="itm",
+        include_vegetation=True,
+    )
+    base = link_service.manual_link_budget(
+        request.tx,
+        request.rx,
+        request.tx.power_dbm,
+        request.tx.gain_dbi,
+        request.rx.gain_dbi,
+        request.rx.sensitivity_dbm,
+        request.frequency_mhz,
+    ).fspl_db
+    monkeypatch.setattr(link_service, "itm_loss", lambda *args, **kwargs: base + 12.0)
+
+    result = link_service.link_budget(request)
+
+    assert result.diffraction_db == 12.0
+    assert result.atmospheric_db == 2.0
+    assert isclose(result.total_loss_db, result.fspl_db + 12.0 + 3.0 + 2.0)
+
+
+def test_p452_link_budget_does_not_double_count_diffraction_or_atmosphere(monkeypatch) -> None:
+    monkeypatch.setattr(link_service, "vegetation_loss_along", lambda *args, **kwargs: 3.0)
+    monkeypatch.setattr(link_service, "atmospheric_loss_between", lambda *args, **kwargs: 99.0)
+    monkeypatch.setattr(link_service, "deygout", lambda *args, **kwargs: 88.0)
+    monkeypatch.setattr(
+        link_service,
+        "surface_profile_from_points",
+        lambda points, *args, **kwargs: SurfaceProfile(
+            distance_m=points[-1].distance_m,
+            samples=[
+                SurfaceSample(
+                    i=index,
+                    lat=point.lat,
+                    lon=point.lon,
+                    distance_m=point.distance_m,
+                    ground_m=0,
+                    building_m=0,
+                    canopy_m=0,
+                    surface_m=0,
+                )
+                for index, point in enumerate(points)
+            ],
+        ),
+    )
+
+    request = LinkBudgetRequest(
+        tx=LinkTx(lat=60.17, lon=24.94, height_agl=30, power_dbm=37, gain_dbi=8),
+        rx=LinkRx(lat=60.25, lon=25.10, height_agl=2, gain_dbi=2, sensitivity_dbm=-110),
+        frequency_mhz=433,
+        model="p452",
+        include_vegetation=True,
+    )
+    base = link_service.manual_link_budget(
+        request.tx,
+        request.rx,
+        request.tx.power_dbm,
+        request.tx.gain_dbi,
+        request.rx.gain_dbi,
+        request.rx.sensitivity_dbm,
+        request.frequency_mhz,
+    ).fspl_db
+    monkeypatch.setattr(link_service, "p452_loss", lambda *args, **kwargs: base + 14.0)
+
+    result = link_service.link_budget(request)
+
+    assert result.diffraction_db == 14.0
+    assert result.atmospheric_db == 0.0
+    assert isclose(result.total_loss_db, result.fspl_db + 14.0 + 3.0)