[Phphtmllib-devel] SF.net SVN: phphtmllib:[3519] trunk/open2300/lib/modules/api/ AviationWeather.inc

[<he...@us...>]

Revision: 3519
          http://phphtmllib.svn.sourceforge.net/phphtmllib/?rev=3519&view=rev
Author:   hemna
Date:     2010-06-28 22:37:47 +0000 (Mon, 28 Jun 2010)

Log Message:
-----------
added density altitude

Modified Paths:
--------------
    trunk/open2300/lib/modules/api/AviationWeather.inc

Modified: trunk/open2300/lib/modules/api/AviationWeather.inc
===================================================================
--- trunk/open2300/lib/modules/api/AviationWeather.inc	2010-06-26 00:17:58 UTC (rev 3518)
+++ trunk/open2300/lib/modules/api/AviationWeather.inc	2010-06-28 22:37:47 UTC (rev 3519)
@@ -703,8 +703,33 @@
 	}
 
 
-	protected function density_altitude() {
+	/**
+	 * 
+	 * @param unknown_type $altitude -- airport altitude
+	 * @param unknown_type $Pmb -- pressure in millibars
+	 * * @param unknown_type $PinHg -- pressure in inches of Mercury
+	 * @param unknown_type $temp -- degress Celcius
+	 * @param unknown_type $dewpoint -- degress Celcius
+	 * @return unknown_type
+	 * 
+	 * @link http://www.4wx.com/wxcalc/formulas/densityAltitude.php
+	 */
+	protected function density_altitude($altitude, $Pmb, $PinHg, $tempC, $dewC) {
+		
+		//get vapor pressure ($Vp)
+		$Vpexp = (7.5*$dewC) / (237.7+$dewC);
+		$Vp = 6.11*pow(10, $Vpexp);	
 
+		//get virtual Temp $Tv (in Kelvin)
+		$TvK = ($tempC / (1-($Vp / $Pmb) * (1-0.622)));
+		
+		//convert temp to Rankine
+		$TvR = (9/5) * ($TvK + 764.84);
+		
+		//get density altitude
+		$Ad = 145366 * ( 1 - pow( ((17.326*$PinHG) / $TvR), 0.235)   );
+		
+		return $Ad;
 	}
 
 


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