@mytec: iter1.6.1 ready for testing

backend/app/services/atmospheric_service.py

@@ -0,0 +1,98 @@
+import math
+
+
+class AtmosphericService:
+    """ITU-R P.676 atmospheric absorption model"""
+
+    # Simplified model for frequencies < 50 GHz
+    # Standard atmosphere: T=15C, P=1013 hPa, humidity=50%
+
+    def calculate_atmospheric_loss(
+        self,
+        frequency_mhz: float,
+        distance_km: float,
+        temperature_c: float = 15.0,
+        humidity_percent: float = 50.0,
+        altitude_m: float = 0.0,
+    ) -> float:
+        """
+        Calculate atmospheric absorption loss
+
+        Args:
+            frequency_mhz: Frequency in MHz
+            distance_km: Path length in km
+            temperature_c: Temperature in Celsius
+            humidity_percent: Relative humidity (0-100)
+            altitude_m: Altitude above sea level
+
+        Returns:
+            Loss in dB
+        """
+        freq_ghz = frequency_mhz / 1000
+
+        # Below 1 GHz - negligible
+        if freq_ghz < 1.0:
+            return 0.0
+
+        # Calculate specific attenuation (dB/km)
+        gamma = self._specific_attenuation(freq_ghz, temperature_c, humidity_percent)
+
+        # Altitude correction (less atmosphere at higher altitudes)
+        altitude_factor = math.exp(-altitude_m / 8500)  # Scale height ~8.5km
+
+        loss = gamma * distance_km * altitude_factor
+
+        return min(loss, 20.0)  # Cap for reasonable distances
+
+    def _specific_attenuation(
+        self,
+        freq_ghz: float,
+        temperature_c: float,
+        humidity_percent: float,
+    ) -> float:
+        """
+        Calculate specific attenuation in dB/km
+
+        Simplified ITU-R P.676 model
+        """
+        # Water vapor density (g/m3) - simplified
+        # Saturation vapor pressure (hPa)
+        es = 6.1121 * math.exp(
+            (18.678 - temperature_c / 234.5)
+            * (temperature_c / (257.14 + temperature_c))
+        )
+        rho = (humidity_percent / 100) * es * 216.7 / (273.15 + temperature_c)
+
+        # Oxygen absorption (dominant at 60 GHz, minor below 10 GHz)
+        if freq_ghz < 10:
+            gamma_o = 0.001 * freq_ghz ** 2  # Very small
+        elif freq_ghz < 57:
+            gamma_o = 0.001 * (freq_ghz / 10) ** 2.5
+        else:
+            # Near 60 GHz resonance
+            gamma_o = 15.0  # Peak absorption
+
+        # Water vapor absorption (peaks at 22 GHz and 183 GHz)
+        if freq_ghz < 10:
+            gamma_w = 0.0001 * rho * freq_ghz ** 2
+        elif freq_ghz < 50:
+            gamma_w = 0.001 * rho * (freq_ghz / 22) ** 2
+        else:
+            gamma_w = 0.01 * rho
+
+        return gamma_o + gamma_w
+
+    @staticmethod
+    def get_weather_description(loss_db: float) -> str:
+        """Describe atmospheric conditions based on loss"""
+        if loss_db < 0.1:
+            return "clear"
+        elif loss_db < 0.5:
+            return "normal"
+        elif loss_db < 2.0:
+            return "humid"
+        else:
+            return "foggy"
+
+
+atmospheric_service = AtmosphericService()