From 9e567cadd6a4e133868765f25125caa7f3fce7bd Mon Sep 17 00:00:00 2001
From: Paul Riseborough <p_riseborough@live.com.au>
Date: Fri, 11 May 2018 15:52:17 +1000
Subject: [PATCH] ekf2: Update parameter description

---
 src/modules/ekf2/ekf2_params.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/modules/ekf2/ekf2_params.c b/src/modules/ekf2/ekf2_params.c
index e6a1c30fae..65a1f16875 100644
--- a/src/modules/ekf2/ekf2_params.c
+++ b/src/modules/ekf2/ekf2_params.c
@@ -1079,7 +1079,12 @@ PARAM_DEFINE_FLOAT(EKF2_MAGB_K, 0.2f);
  *
  * If this parameter is enabled then the estimator will make use of the range finder measurements
  * to estimate it's height even if range sensor is not the primary height source. It will only do so if conditions
- * for range measurement fusion are met.
+ * for range measurement fusion are met. This enables the range finder to be used during low speed and low altitude
+ * operation. Speed and height criteria are controlled by EKF2_RNG_A_VMAX and EKF2_RNG_A_HMAX.
+ * It should not be used for terrain following. It is intended to be used where a vertical takeoff and landing
+ * is performed, and horizontal flight does not occur until above EKF2_RNG_A_HMAX. If vehicle motion causes
+ * repeated switvhing between the rimary height sensor and range finder, an offset in the local position origin
+ * can accumulate. For terrain following, it is recommended to use the MPC_ALT_MODE parameter instead.
  *
  * @group EKF2
  * @value 0 Range aid disabled
-- 
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