From 9fe3abf5ca59a67fb570179b6b78f32e228cc20d Mon Sep 17 00:00:00 2001
From: Daniel Nugent <djnugent@iastate.edu>
Date: Fri, 11 Sep 2015 18:15:02 +0900
Subject: [PATCH] Copter: precision landing uses sonar alt if available

---
 ArduCopter/precision_landing.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/ArduCopter/precision_landing.cpp b/ArduCopter/precision_landing.cpp
index c793e2e76a..eb938145df 100644
--- a/ArduCopter/precision_landing.cpp
+++ b/ArduCopter/precision_landing.cpp
@@ -15,10 +15,16 @@ void Copter::init_precland()
 
 void Copter::update_precland()
 {
-    copter.precland.update(current_loc.alt);
+    float final_alt = current_loc.alt;
+
+    // use range finder altitude if it is valid
+    if (sonar_enabled && (sonar_alt_health >= SONAR_ALT_HEALTH_MAX)) {
+        final_alt = sonar_alt;
+    }
+
+    copter.precland.update(final_alt);
 
     // log output
     Log_Write_Precland();
 }
-
 #endif