From e6ed1e5dbd41e95190f5015e2c5b2aeaa88e0efb Mon Sep 17 00:00:00 2001
From: ulteq <ulteq@web.de>
Date: Fri, 15 May 2015 19:00:11 +0200
Subject: [PATCH] Added utility functions to calculate heat index and wind
 chill

---
 addons/weather/XEH_preInit.sqf                |  2 ++
 .../functions/fnc_calculateHeatIndex.sqf      | 23 +++++++++++++++++++
 .../functions/fnc_calculateWindChill.sqf      | 22 ++++++++++++++++++
 addons/weather/script_component.hpp           | 11 +++++++++
 4 files changed, 58 insertions(+)
 create mode 100644 addons/weather/functions/fnc_calculateHeatIndex.sqf
 create mode 100644 addons/weather/functions/fnc_calculateWindChill.sqf

diff --git a/addons/weather/XEH_preInit.sqf b/addons/weather/XEH_preInit.sqf
index 85166ce356..453c7e57b4 100644
--- a/addons/weather/XEH_preInit.sqf
+++ b/addons/weather/XEH_preInit.sqf
@@ -5,8 +5,10 @@ ADDON = false;
 
 PREP(calculateAirDensity);
 PREP(calculateBarometricPressure);
+PREP(calculateHeatIndex);
 PREP(calculateRoughnessLength);
 PREP(calculateTemperatureAtHeight);
+PREP(calculateWindChill);
 PREP(calculateWindSpeed);
 PREP(displayWindInfo);
 PREP(getMapData);
diff --git a/addons/weather/functions/fnc_calculateHeatIndex.sqf b/addons/weather/functions/fnc_calculateHeatIndex.sqf
new file mode 100644
index 0000000000..4515a85a7a
--- /dev/null
+++ b/addons/weather/functions/fnc_calculateHeatIndex.sqf
@@ -0,0 +1,23 @@
+/*
+ * Author: Ruthberg
+ *
+ * Calculates heat index based on temperature and humidity
+ *
+ * Arguments:
+ * 0: temperature - degrees celcius <NUMBER>
+ * 2: relativeHumidity - value between 0.0 and 1.0 <NUMBER>
+ *
+ * Return Value:
+ * 0: heat index <NUMBER>
+ *
+ * Return value:
+ * None
+ */
+#include "script_component.hpp"
+
+PARAMS_2(_t, _rh);
+
+_rh = _rh * 100; // relative humidity in %
+
+// Source: https://en.wikipedia.org/wiki/Heat_index
+(__C1 + __C2 * _t + __C3 * _rh + __C4 * _t * _rh + __C5 * _t^2 + __C6 * _rh^2 + __C7 * _t^2 * _rh + __C8 * _t * _rh^2 + __C9 * _t^2 * _rh^2)
diff --git a/addons/weather/functions/fnc_calculateWindChill.sqf b/addons/weather/functions/fnc_calculateWindChill.sqf
new file mode 100644
index 0000000000..0eb63e9701
--- /dev/null
+++ b/addons/weather/functions/fnc_calculateWindChill.sqf
@@ -0,0 +1,22 @@
+/*
+ * Author: Ruthberg
+ *
+ * Calculates wind chill based on temperature and wind speed
+ *
+ * Arguments:
+ * 0: temperature - degrees celcius <NUMBER>
+ * 2: wind speed - m/s <NUMBER>
+ *
+ * Return Value:
+ * 0: wind chill <NUMBER>
+ *
+ * Public: No
+ */
+#include "script_component.hpp"
+
+PARAMS_2(_t, _v);
+
+_v = _v * 3,6; // wind speed in km/h
+
+// Source: https://en.wikipedia.org/wiki/Wind_chill
+(13.12 + 0.06215 * _t - 11.37 * _v ^ 0.16 + 0.3965 * _t * _v^0.16)
diff --git a/addons/weather/script_component.hpp b/addons/weather/script_component.hpp
index edc1ac64d0..e5a7a74f39 100644
--- a/addons/weather/script_component.hpp
+++ b/addons/weather/script_component.hpp
@@ -18,3 +18,14 @@
 #define WATER_VAPOR_MOLAR_MASS 0.018016
 #define DRY_AIR_MOLAR_MASS 0.028964
 #define SPECIFIC_GAS_CONSTANT_DRY_AIR 287.058
+
+// Heat index coefficients
+#define __C1 −8.784695
+#define __C2 1.61139411
+#define __C3 2.338549
+#define __C4 −0.14611605
+#define __C5 −1.2308094 · 10^(−2)
+#define __C6 −1.6424828 · 10^(−2)
+#define __C7 2.211732 · 10^(−3)
+#define __C8 7.2546 · 10^(−4)
+#define __C9 −3.582 · 10^(−6)