diff --git a/src/blackmisc/simulation/interpolator.cpp b/src/blackmisc/simulation/interpolator.cpp
index 71a431f50..17735004c 100644
--- a/src/blackmisc/simulation/interpolator.cpp
+++ b/src/blackmisc/simulation/interpolator.cpp
@@ -258,7 +258,13 @@ namespace BlackMisc::Simulation
 
             // use derived interpolant function
             const bool interpolateGndFlag = pbh.getEndSituation().hasGroundDetailsForGndInterpolation() && pbh.getStartSituation().hasGroundDetailsForGndInterpolation();
-            currentSituation = interpolant.interpolatePositionAndAltitude(currentSituation, interpolateGndFlag);
+            currentSituation = interpolant.interpolatePositionAndAltitude(currentSituation);
+
+            if (interpolateGndFlag)
+            {
+                currentSituation.setOnGroundInfo(interpolant.interpolateGroundFactor());
+            }
+
             if (currentSituation.isNull()) { break; }
 
             // if we get here and the vector is invalid it means we haven't handled it correctly in one of the interpolators
diff --git a/src/blackmisc/simulation/interpolatorlinear.cpp b/src/blackmisc/simulation/interpolatorlinear.cpp
index 4e7a32468..9730634d3 100644
--- a/src/blackmisc/simulation/interpolatorlinear.cpp
+++ b/src/blackmisc/simulation/interpolatorlinear.cpp
@@ -45,7 +45,7 @@ namespace BlackMisc::Simulation
     void CInterpolatorLinear::anchor()
     {}
 
-    CAircraftSituation CInterpolatorLinear::CInterpolant::interpolatePositionAndAltitude(const CAircraftSituation &situation, bool interpolateGndFactor) const
+    CAircraftSituation CInterpolatorLinear::CInterpolant::interpolatePositionAndAltitude(const CAircraftSituation &situation) const
     {
         const std::array<double, 3> startVec(m_startSituation.getPosition().normalVectorDouble());
         const std::array<double, 3> endVec(m_endSituation.getPosition().normalVectorDouble());
@@ -82,27 +82,29 @@ namespace BlackMisc::Simulation
         interpolatedSituation.setAltitude(altitude);
         interpolatedSituation.setMSecsSinceEpoch(this->getInterpolatedTime());
 
-        if (interpolateGndFactor)
-        {
-            const double startGroundFactor = m_startSituation.getOnGroundInfo().getGroundFactor();
-            const double endGroundFactor = m_endSituation.getOnGroundInfo().getGroundFactor();
-            if (CAircraftSituation::isGfEqualAirborne(startGroundFactor, endGroundFactor))
-            {
-                interpolatedSituation.setOnGroundInfo({ COnGroundInfo::NotOnGround, COnGroundInfo::OnGroundByInterpolation });
-            }
-            else if (CAircraftSituation::isGfEqualOnGround(startGroundFactor, endGroundFactor))
-            {
-                interpolatedSituation.setOnGroundInfo({ COnGroundInfo::OnGround, COnGroundInfo::OnGroundByInterpolation });
-            }
-            else
-            {
-                const double interpolatedGroundFactor = (endGroundFactor - startGroundFactor) * tf + startGroundFactor;
-                interpolatedSituation.setOnGroundInfo(COnGroundInfo(interpolatedGroundFactor));
-            }
-        }
         return interpolatedSituation;
     }
 
+    Aviation::COnGroundInfo CInterpolatorLinear::CInterpolant::interpolateGroundFactor() const
+    {
+        const double startGroundFactor = m_startSituation.getOnGroundInfo().getGroundFactor();
+        const double endGroundFactor = m_endSituation.getOnGroundInfo().getGroundFactor();
+        if (CAircraftSituation::isGfEqualAirborne(startGroundFactor, endGroundFactor))
+        {
+            return { COnGroundInfo::NotOnGround, COnGroundInfo::OnGroundByInterpolation };
+        }
+        else if (CAircraftSituation::isGfEqualOnGround(startGroundFactor, endGroundFactor))
+        {
+            return { COnGroundInfo::OnGround, COnGroundInfo::OnGroundByInterpolation };
+        }
+        else
+        {
+            const double tf = clampValidTimeFraction(m_simulationTimeFraction);
+            const double interpolatedGroundFactor = (endGroundFactor - startGroundFactor) * tf + startGroundFactor;
+            return COnGroundInfo(interpolatedGroundFactor);
+        }
+    }
+
     CInterpolatorLinear::CInterpolant CInterpolatorLinear::getInterpolant(SituationLog &log)
     {
         // set default situations
diff --git a/src/blackmisc/simulation/interpolatorlinear.h b/src/blackmisc/simulation/interpolatorlinear.h
index 73d38773e..c39cf3cb2 100644
--- a/src/blackmisc/simulation/interpolatorlinear.h
+++ b/src/blackmisc/simulation/interpolatorlinear.h
@@ -49,9 +49,11 @@ namespace BlackMisc
 
                 //! Perform the interpolation
                 //! \param situation situation used as a base for interpolation. Contains for example the already interpolated PBH.
-                //! \param interpolateGndFactor whether to interpolate the GND factor.
-                //! \return \p situation with interpolated position and altitude, updated timestamp and possibly interpolated GND factor
-                Aviation::CAircraftSituation interpolatePositionAndAltitude(const Aviation::CAircraftSituation &situation, bool interpolateGndFactor) const;
+                //! \return \p situation with interpolated position and altitude and updated timestamp
+                Aviation::CAircraftSituation interpolatePositionAndAltitude(const Aviation::CAircraftSituation &situation) const;
+
+                //! Interpolate the ground information/factor
+                Aviation::COnGroundInfo interpolateGroundFactor() const;
 
                 //! Start situation
                 const Aviation::CAircraftSituation &getStartSituation() const { return m_startSituation; }
diff --git a/src/blackmisc/simulation/interpolatorspline.cpp b/src/blackmisc/simulation/interpolatorspline.cpp
index 0fbbcdebe..c7f2fca89 100644
--- a/src/blackmisc/simulation/interpolatorspline.cpp
+++ b/src/blackmisc/simulation/interpolatorspline.cpp
@@ -315,7 +315,7 @@ namespace BlackMisc::Simulation
         m_situationsAvailable = pa.size();
     }
 
-    CAircraftSituation CInterpolatorSpline::CInterpolant::interpolatePositionAndAltitude(const CAircraftSituation &currentSituation, bool interpolateGndFactor) const
+    CAircraftSituation CInterpolatorSpline::CInterpolant::interpolatePositionAndAltitude(const CAircraftSituation &currentSituation) const
     {
         const double t1 = m_pa.t[1];
         const double t2 = m_pa.t[2]; // latest (adjusted)
@@ -361,28 +361,34 @@ namespace BlackMisc::Simulation
         newSituation.setAltitude(alt);
         newSituation.setMSecsSinceEpoch(this->getInterpolatedTime());
 
-        if (interpolateGndFactor)
-        {
-            const double gnd1 = m_pa.gnd[1];
-            const double gnd2 = m_pa.gnd[2]; // latest
-
-            if (CAircraftSituation::isGfEqualAirborne(gnd1, gnd2))
-            {
-                newSituation.setOnGroundInfo({ COnGroundInfo::NotOnGround, COnGroundInfo::OnGroundByInterpolation });
-            }
-            else if (CAircraftSituation::isGfEqualOnGround(gnd1, gnd2))
-            {
-                newSituation.setOnGroundInfo({ COnGroundInfo::OnGround, COnGroundInfo::OnGroundByInterpolation });
-            }
-            else
-            {
-                const double newGnd = evalSplineInterval(m_currentTimeMsSinceEpoc, t1, t2, gnd1, gnd2, m_pa.dgnd[1], m_pa.dgnd[2]);
-                newSituation.setOnGroundInfo(COnGroundInfo(newGnd));
-            }
-        }
         return newSituation;
     }
 
+    Aviation::COnGroundInfo CInterpolatorSpline::CInterpolant::interpolateGroundFactor() const
+    {
+        const double t1 = m_pa.t[1];
+        const double t2 = m_pa.t[2]; // latest (adjusted)
+        bool valid = (t1 < t2) && (m_currentTimeMsSinceEpoc >= t1) && (m_currentTimeMsSinceEpoc < t2);
+        if (!valid) { return { COnGroundInfo::OnGroundSituationUnknown, COnGroundInfo::NotSetGroundDetails }; }
+
+        const double gnd1 = m_pa.gnd[1];
+        const double gnd2 = m_pa.gnd[2]; // latest
+
+        if (CAircraftSituation::isGfEqualAirborne(gnd1, gnd2))
+        {
+            return { COnGroundInfo::NotOnGround, COnGroundInfo::OnGroundByInterpolation };
+        }
+        else if (CAircraftSituation::isGfEqualOnGround(gnd1, gnd2))
+        {
+            return { COnGroundInfo::OnGround, COnGroundInfo::OnGroundByInterpolation };
+        }
+        else
+        {
+            const double newGnd = evalSplineInterval(m_currentTimeMsSinceEpoc, t1, t2, gnd1, gnd2, m_pa.dgnd[1], m_pa.dgnd[2]);
+            return COnGroundInfo(newGnd);
+        }
+    }
+
     void CInterpolatorSpline::CInterpolant::setTimes(qint64 currentTimeMs, double timeFraction, qint64 interpolatedTimeMs)
     {
         m_currentTimeMsSinceEpoc = currentTimeMs;
diff --git a/src/blackmisc/simulation/interpolatorspline.h b/src/blackmisc/simulation/interpolatorspline.h
index 710e492a0..6721a1a63 100644
--- a/src/blackmisc/simulation/interpolatorspline.h
+++ b/src/blackmisc/simulation/interpolatorspline.h
@@ -65,9 +65,11 @@ namespace BlackMisc::Simulation
 
             //! Perform the interpolation
             //! \param situation situation used as a base for interpolation. Contains for example the already interpolated PBH.
-            //! \param interpolateGndFactor whether to interpolate the GND factor.
-            //! \return \p situation with interpolated position and altitude, updated timestamp and possibly interpolated GND factor
-            Aviation::CAircraftSituation interpolatePositionAndAltitude(const Aviation::CAircraftSituation &currentSituation, bool interpolateGndFactor) const;
+            //! \return \p situation with interpolated position and altitude and updated timestamp
+            Aviation::CAircraftSituation interpolatePositionAndAltitude(const Aviation::CAircraftSituation &currentSituation) const;
+
+            //! Interpolate the ground information/factor
+            Aviation::COnGroundInfo interpolateGroundFactor() const;
 
             //! Set the time values
             void setTimes(qint64 currentTimeMs, double timeFraction, qint64 interpolatedTimeMs);