From d293c4231ded671d6c87a71d77641501e3172161 Mon Sep 17 00:00:00 2001
From: Paul Riseborough <p_riseborough@live.com.au>
Date: Wed, 11 Oct 2017 21:54:47 +1100
Subject: [PATCH] EKF: Protect against divide by zero caused by invalid optical
 flow

---
 EKF/estimator_interface.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/EKF/estimator_interface.cpp b/EKF/estimator_interface.cpp
index 283b435630..3b28b99297 100644
--- a/EKF/estimator_interface.cpp
+++ b/EKF/estimator_interface.cpp
@@ -278,7 +278,13 @@ void EstimatorInterface::setOpticalFlowData(uint64_t time_usec, flow_message *fl
 		// check if enough integration time and fail if integration time is less than 50%
 		// of min arrival interval because too much data is being lost
 		float delta_time = 1e-6f * (float)flow->dt;
-		bool delta_time_good = (delta_time >= 5e-7f * (float)_min_obs_interval_us);
+		float delta_time_min = 5e-7f * (float)_min_obs_interval_us;
+		bool delta_time_good = delta_time >= delta_time_min;
+		if (!delta_time_good) {
+			// protect against overflow casued by division with very small delta_time
+			delta_time = delta_time_min;
+		}
+
 
 		// check magnitude is within sensor limits
 		float flow_rate_magnitude;