From e26711af7d98811433ffd566ebe957dc07c26dfb Mon Sep 17 00:00:00 2001
From: Paul Riseborough <p_riseborough@live.com.au>
Date: Sat, 5 May 2018 16:34:55 +1000
Subject: [PATCH] EKF: relax terrain update requirements for continuing optical
 flow use

---
 EKF/control.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/EKF/control.cpp b/EKF/control.cpp
index 04cb8c974b..795a0bef23 100644
--- a/EKF/control.cpp
+++ b/EKF/control.cpp
@@ -441,8 +441,8 @@ void Ekf::controlOpticalFlowFusion()
 			}
 		}
 
-		// fuse the data if the terrain/distance to bottom is valid
-		if (_control_status.flags.opt_flow && get_terrain_valid()) {
+		// fuse the data if the terrain/distance to bottom is valid but use a more relaxed check to enable it to survive bad range finder data
+		if (_control_status.flags.opt_flow && (_time_last_imu - _time_last_hagl_fuse < (uint64_t)10e6)) {
 			// Update optical flow bias estimates
 			calcOptFlowBias();