new library for atmosphere calculations

Signed-off-by: RomanBapst <bapstroman@gmail.com>
2026-10-26 07:43:33 +08:00 · 2023-10-21 12:25:45 -05:00
parent f120ebcdc0
commit ecb78ca207
10 changed files with 341 additions and 57 deletions
@@ -0,0 +1,81 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2023 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file atmosphere.cpp
+ *
+ */
+
+#include <geo/geo.h>
+#include "atmosphere.h"
+namespace atmosphere
+{
+
+static constexpr float kTempRefKelvin = 15.f - CONSTANTS_ABSOLUTE_NULL_CELSIUS; // temperature at base height in Kelvin
+static constexpr float kTempGradient = -6.5f / 1000.f; // temperature gradient in degrees per meter
+static constexpr float kPressRefSeaLevelPa = 101325.f; // pressure at sea level in Pa
+
+float getDensityFromPressureAndTemp(const float pressure_pa, const float temperature_celsius)
+{
+	return (pressure_pa / (CONSTANTS_AIR_GAS_CONST * (temperature_celsius - CONSTANTS_ABSOLUTE_NULL_CELSIUS)));
+}
+float getPressureFromAltitude(const float altitude_m)
+{
+
+	return kPressRefSeaLevelPa * powf((altitude_m * kTempGradient + kTempRefKelvin) / kTempRefKelvin,
+					  -CONSTANTS_ONE_G / (kTempGradient * CONSTANTS_AIR_GAS_CONST));
+}
+float getAltitudeFromPressure(float pressure_pa, float pressure_sealevel_pa)
+{
+	// calculate altitude using the hypsometric equation
+
+	const float pressure_ratio = pressure_pa / pressure_sealevel_pa;
+
+	/*
+	 * Solve:
+	 *
+	 *     /        -(aR / g)     \
+	 *    | (p / p1)          . T1 | - T1
+	 *     \                      /
+	 * h = -------------------------------  + h1
+	 *                   a
+	 */
+	return (((powf(pressure_ratio, (-(kTempGradient * CONSTANTS_AIR_GAS_CONST) / CONSTANTS_ONE_G))) * kTempRefKelvin) -
+		kTempRefKelvin) / kTempGradient;
+
+}
+float getStandardTemperatureAtAltitude(float altitude_m)
+{
+	return 15.0f + kTempGradient * altitude_m;
+}
+}