diff --git a/src/blackmisc/simulation/interpolator.cpp b/src/blackmisc/simulation/interpolator.cpp
index e74fc41f6..48465d348 100644
--- a/src/blackmisc/simulation/interpolator.cpp
+++ b/src/blackmisc/simulation/interpolator.cpp
@@ -153,43 +153,6 @@ namespace BlackMisc::Simulation
         this->initCorrespondingModel();
     }
 
-    bool CInterpolator::verifyInterpolationSituations(const CAircraftSituation &oldest, const CAircraftSituation &newer, const CAircraftSituation &latest, const CInterpolationAndRenderingSetupPerCallsign &setup)
-    {
-        if (!CBuildConfig::isLocalDeveloperDebugBuild()) { return true; }
-        CAircraftSituationList situations;
-
-        // oldest last, null ignored
-        if (!latest.isNull()) { situations.push_back(latest); }
-        if (!newer.isNull()) { situations.push_back(newer); }
-        if (!oldest.isNull()) { situations.push_back(oldest); }
-
-        const bool sorted = situations.isSortedAdjustedLatestFirstWithoutNullPositions();
-        if (setup.isNull() || !setup.isAircraftPartsEnabled()) { return sorted; }
-
-        bool details = false;
-        if (situations.containsOnGroundDetails(COnGroundInfo::InFromParts))
-        {
-            // if a client supports parts, all ground situations are supposed to be parts based
-            details = situations.areAllOnGroundDetailsSame(COnGroundInfo::InFromParts);
-            BLACK_VERIFY_X(details, Q_FUNC_INFO, "Once gnd.from parts -> always gnd. from parts");
-        }
-
-        for (const CAircraftSituation &s : situations)
-        {
-            if (!s.hasGroundElevation()) { continue; }
-            BLACK_VERIFY_X(!s.getGroundElevation().isZeroEpsilonConsidered(), Q_FUNC_INFO, "Suspicous 0 gnd. value");
-        }
-
-        // check if middle situation is missing
-        if (latest.hasGroundElevation() && oldest.hasGroundElevation())
-        {
-            BLACK_VERIFY_X(newer.hasGroundElevation(), Q_FUNC_INFO, "Middle ground elevation is missing");
-        }
-
-        // result
-        return sorted && details;
-    }
-
     const QStringList &CInterpolator::getLogCategories()
     {
         static const QStringList cats { CLogCategories::interpolator() };
diff --git a/src/blackmisc/simulation/interpolator.h b/src/blackmisc/simulation/interpolator.h
index a929ed75e..282fd7e9f 100644
--- a/src/blackmisc/simulation/interpolator.h
+++ b/src/blackmisc/simulation/interpolator.h
@@ -145,10 +145,6 @@ namespace BlackMisc::Simulation
 
         bool m_unitTest = false; //!< mark as unit test
 
-        //! Verify gnd flag, times, ... true means "OK"
-        bool verifyInterpolationSituations(const Aviation::CAircraftSituation &oldest, const Aviation::CAircraftSituation &newer, const Aviation::CAircraftSituation &latest,
-                                           const CInterpolationAndRenderingSetupPerCallsign &setup = CInterpolationAndRenderingSetupPerCallsign::null());
-
     private:
         CInterpolationLogger *m_logger = nullptr; //!< optional interpolation logger
         QTimer m_initTimer; //!< timer to init model, will be deleted when interpolator is deleted and cancel the call
diff --git a/src/blackmisc/simulation/interpolatorspline.cpp b/src/blackmisc/simulation/interpolatorspline.cpp
index 717974535..da3f66188 100644
--- a/src/blackmisc/simulation/interpolatorspline.cpp
+++ b/src/blackmisc/simulation/interpolatorspline.cpp
@@ -159,7 +159,7 @@ namespace BlackMisc::Simulation
 
         if (CBuildConfig::isLocalDeveloperDebugBuild())
         {
-            const bool verified = this->verifyInterpolationSituations(m_s[0], m_s[1], m_s[2]); // oldest -> latest, only verify order
+            const bool verified = verifyInterpolationSituations(m_s[0], m_s[1], m_s[2]); // oldest -> latest, only verify order
             if (!verified)
             {
                 static const QString vm("Unverified situations, m0-2 (oldest latest) %1 %2 %3");
@@ -418,4 +418,42 @@ namespace BlackMisc::Simulation
         }();
         return pa;
     }
+
+    bool CInterpolatorSpline::verifyInterpolationSituations(const CAircraftSituation &oldest, const CAircraftSituation &newer, const CAircraftSituation &latest, const CInterpolationAndRenderingSetupPerCallsign &setup)
+    {
+        if (!CBuildConfig::isLocalDeveloperDebugBuild()) { return true; }
+        CAircraftSituationList situations;
+
+        // oldest last, null ignored
+        if (!latest.isNull()) { situations.push_back(latest); }
+        if (!newer.isNull()) { situations.push_back(newer); }
+        if (!oldest.isNull()) { situations.push_back(oldest); }
+
+        const bool sorted = situations.isSortedAdjustedLatestFirstWithoutNullPositions();
+        if (setup.isNull() || !setup.isAircraftPartsEnabled()) { return sorted; }
+
+        bool details = false;
+        if (situations.containsOnGroundDetails(COnGroundInfo::InFromParts))
+        {
+            // if a client supports parts, all ground situations are supposed to be parts based
+            details = situations.areAllOnGroundDetailsSame(COnGroundInfo::InFromParts);
+            BLACK_VERIFY_X(details, Q_FUNC_INFO, "Once gnd.from parts -> always gnd. from parts");
+        }
+
+        for (const CAircraftSituation &s : situations)
+        {
+            if (!s.hasGroundElevation()) { continue; }
+            BLACK_VERIFY_X(!s.getGroundElevation().isZeroEpsilonConsidered(), Q_FUNC_INFO, "Suspicous 0 gnd. value");
+        }
+
+        // check if middle situation is missing
+        if (latest.hasGroundElevation() && oldest.hasGroundElevation())
+        {
+            BLACK_VERIFY_X(newer.hasGroundElevation(), Q_FUNC_INFO, "Middle ground elevation is missing");
+        }
+
+        // result
+        return sorted && details;
+    }
+
 } // ns
diff --git a/src/blackmisc/simulation/interpolatorspline.h b/src/blackmisc/simulation/interpolatorspline.h
index 325c2a2ee..9c13cedc6 100644
--- a/src/blackmisc/simulation/interpolatorspline.h
+++ b/src/blackmisc/simulation/interpolatorspline.h
@@ -101,6 +101,10 @@ namespace BlackMisc::Simulation
         //! Fill the situations array
         bool fillSituationsArray();
 
+        //! Verify gnd flag, times, ... true means "OK"
+        static bool verifyInterpolationSituations(const Aviation::CAircraftSituation &oldest, const Aviation::CAircraftSituation &newer, const Aviation::CAircraftSituation &latest,
+                                                  const CInterpolationAndRenderingSetupPerCallsign &setup = CInterpolationAndRenderingSetupPerCallsign::null());
+
         qint64 m_prevSampleAdjustedTime = 0; //!< previous sample time + offset
         qint64 m_nextSampleAdjustedTime = 0; //!< previous sample time + offset
         qint64 m_prevSampleTime = 0; //!< previous sample "real time"