From 85b87b752ab90157eb7cbd826d568f818ff1d4d2 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Mon, 19 Nov 2012 07:10:26 +1100
Subject: [PATCH] APM: change WIND direction to match convention

Thanks to Leo Hogg for pointing this out
---
 ArduPlane/GCS_Mavlink.pde                                   | 3 ++-
 libraries/GCS_MAVLink/message_definitions/ardupilotmega.xml | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/ArduPlane/GCS_Mavlink.pde b/ArduPlane/GCS_Mavlink.pde
index fb8f54138f..5e57e2ca0c 100644
--- a/ArduPlane/GCS_Mavlink.pde
+++ b/ArduPlane/GCS_Mavlink.pde
@@ -455,7 +455,8 @@ static void NOINLINE send_wind(mavlink_channel_t chan)
     Vector3f wind = ahrs.wind_estimate();
     mavlink_msg_wind_send(
         chan,
-        degrees(atan2(wind.y, wind.x)),
+        degrees(atan2(-wind.y, -wind.x)), // use negative, to give
+                                          // direction wind is coming from
         sqrt(sq(wind.x)+sq(wind.y)),
         wind.z);
 }
diff --git a/libraries/GCS_MAVLink/message_definitions/ardupilotmega.xml b/libraries/GCS_MAVLink/message_definitions/ardupilotmega.xml
index 8ac0b1d523..533b0c51bb 100644
--- a/libraries/GCS_MAVLink/message_definitions/ardupilotmega.xml
+++ b/libraries/GCS_MAVLink/message_definitions/ardupilotmega.xml
@@ -306,7 +306,7 @@
 
 	  <message name="WIND" id="168">
 	    <description>Wind estimation</description>
-            <field type="float" name="direction">wind direction (degrees)</field>
+            <field type="float" name="direction">wind direction that wind is coming from (degrees)</field>
             <field type="float" name="speed">wind speed in ground plane (m/s)</field>
             <field type="float" name="speed_z">vertical wind speed (m/s)</field>
 	  </message>