From 1b381b56752c83e6348b914abb700e5d7501a75b Mon Sep 17 00:00:00 2001
From: Randy Mackay <rmackay9@yahoo.com>
Date: Wed, 29 Apr 2015 14:12:41 +0900
Subject: [PATCH] Baro: get_air_density_ratio gets div-by-zero check

---
 libraries/AP_Baro/AP_Baro.cpp | 9 +++++++--
 libraries/AP_Baro/AP_Baro.h   | 2 +-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/libraries/AP_Baro/AP_Baro.cpp b/libraries/AP_Baro/AP_Baro.cpp
index f412fe4f5b..1f5aa1384a 100644
--- a/libraries/AP_Baro/AP_Baro.cpp
+++ b/libraries/AP_Baro/AP_Baro.cpp
@@ -208,10 +208,15 @@ float AP_Baro::get_EAS2TAS(void)
     return _EAS2TAS;
 }
 
-// return air density / sea level density - decreases in altitude
+// return air density / sea level density - decreases as altitude climbs
 float AP_Baro::get_air_density_ratio(void)
 {
-    return 1.0f/(sq(get_EAS2TAS()));
+    float eas2tas = get_EAS2TAS();
+    if (eas2tas > 0.0f) {
+        return 1.0f/(sq(get_EAS2TAS()));
+    } else {
+        return 1.0f;
+    }
 }
 
 // return current climb_rate estimeate relative to time that calibrate()
diff --git a/libraries/AP_Baro/AP_Baro.h b/libraries/AP_Baro/AP_Baro.h
index 6a0eed037b..00d035ad6f 100644
--- a/libraries/AP_Baro/AP_Baro.h
+++ b/libraries/AP_Baro/AP_Baro.h
@@ -79,7 +79,7 @@ public:
     // get scale factor required to convert equivalent to true airspeed
     float get_EAS2TAS(void);
 
-    // get air density / sea level density - decreases in altitude
+    // get air density / sea level density - decreases as altitude climbs
     float get_air_density_ratio(void);
 
     // get current climb rate in meters/s. A positive number means