diff --git a/src/blackcore/airspacemonitor.cpp b/src/blackcore/airspacemonitor.cpp
index 2b654d125..d28e6147a 100644
--- a/src/blackcore/airspacemonitor.cpp
+++ b/src/blackcore/airspacemonitor.cpp
@@ -274,7 +274,7 @@ namespace BlackCore
     bool CAirspaceMonitor::updateAircraftGroundElevation(const CCallsign &callsign, const CElevationPlane &elevation)
     {
         QWriteLocker l(&m_lockAircraft);
-        const int c = m_aircraftInRange.setGroundElevation(callsign, elevation.geodeticHeight());
+        const int c = m_aircraftInRange.setGroundElevationChecked(callsign, elevation);
         return c > 0;
     }
 
@@ -1230,7 +1230,7 @@ namespace BlackCore
         Q_ASSERT(CThreadUtils::isCurrentThreadObjectThread(this));
 
         // update
-        const CPropertyIndexVariantMap vm( {CSimulatedAircraft::IndexCom1System, CComSystem::IndexActiveFrequency}, CVariant::from(frequency));
+        const CPropertyIndexVariantMap vm({CSimulatedAircraft::IndexCom1System, CComSystem::IndexActiveFrequency}, CVariant::from(frequency));
         this->updateAircraftInRange(callsign, vm);
     }
 
diff --git a/src/blackmisc/aviation/aircraftsituation.cpp b/src/blackmisc/aviation/aircraftsituation.cpp
index 67e358ffd..28d452fcb 100644
--- a/src/blackmisc/aviation/aircraftsituation.cpp
+++ b/src/blackmisc/aviation/aircraftsituation.cpp
@@ -8,6 +8,7 @@
  */
 
 #include "blackmisc/aviation/aircraftsituation.h"
+#include "blackmisc/aviation/aircraftpartslist.h"
 #include "blackmisc/geo/elevationplane.h"
 #include "blackmisc/pq/physicalquantity.h"
 #include "blackmisc/pq/units.h"
@@ -18,7 +19,6 @@
 #include "QStringBuilder"
 #include <QtGlobal>
 
-using namespace BlackMisc;
 using namespace BlackMisc::PhysicalQuantities;
 using namespace BlackMisc::Geo;
 
@@ -26,24 +26,22 @@ namespace BlackMisc
 {
     namespace Aviation
     {
-        CAircraftSituation::CAircraftSituation()
-            : m_groundElevation({ 0, nullptr }, CAltitude::MeanSeaLevel) {}
+        CAircraftSituation::CAircraftSituation() {}
 
-        CAircraftSituation::CAircraftSituation(const CCallsign &correspondingCallsign)
-            : m_correspondingCallsign(correspondingCallsign), m_groundElevation({ 0, nullptr }, CAltitude::MeanSeaLevel)
+        CAircraftSituation::CAircraftSituation(const CCallsign &correspondingCallsign) : m_correspondingCallsign(correspondingCallsign)
         {}
 
-        CAircraftSituation::CAircraftSituation(const CCoordinateGeodetic &position, const CHeading &heading, const CAngle &pitch, const CAngle &bank, const CSpeed &gs, const CAltitude &groundElevation)
+        CAircraftSituation::CAircraftSituation(const CCoordinateGeodetic &position, const CHeading &heading, const CAngle &pitch, const CAngle &bank, const CSpeed &gs, const CElevationPlane &groundElevation)
             : m_position(position), m_heading(heading), m_pitch(pitch),
-              m_bank(bank), m_groundSpeed(gs), m_groundElevation(groundElevation)
+              m_bank(bank), m_groundSpeed(gs), m_groundElevationPlane(groundElevation)
         {
             m_pressureAltitude = position.geodeticHeight().toPressureAltitude(CPressure(1013.25, CPressureUnit::mbar()));
         }
 
-        CAircraftSituation::CAircraftSituation(const CCallsign &correspondingCallsign, const CCoordinateGeodetic &position, const CHeading &heading, const CAngle &pitch, const CAngle &bank, const CSpeed &gs, const CAltitude &groundElevation)
+        CAircraftSituation::CAircraftSituation(const CCallsign &correspondingCallsign, const CCoordinateGeodetic &position, const CHeading &heading, const CAngle &pitch, const CAngle &bank, const CSpeed &gs, const CElevationPlane &groundElevation)
             : m_correspondingCallsign(correspondingCallsign),
               m_position(position), m_heading(heading), m_pitch(pitch),
-              m_bank(bank), m_groundSpeed(gs), m_groundElevation(groundElevation)
+              m_bank(bank), m_groundSpeed(gs), m_groundElevationPlane(groundElevation)
         {
             m_correspondingCallsign.setTypeHint(CCallsign::Aircraft);
             m_pressureAltitude = position.geodeticHeight().toPressureAltitude(CPressure(1013.25, CPressureUnit::mbar()));
@@ -59,7 +57,7 @@ namespace BlackMisc
                    QStringLiteral(" og: ") % this->getOnGroundInfo() %
                    QStringLiteral(" gs: ") % m_groundSpeed.valueRoundedWithUnit(CSpeedUnit::kts(), 1, true) %
                    QStringLiteral(" ") % m_groundSpeed.valueRoundedWithUnit(CSpeedUnit::m_s(), 1, true) %
-                   QStringLiteral(" elevation: ") % (m_groundElevation.toQString(i18n));
+                   QStringLiteral(" elevation: ") % (m_groundElevationPlane.toQString(i18n));
         }
 
         const QString &CAircraftSituation::isOnGroundToString(CAircraftSituation::IsOnGround onGround)
@@ -96,7 +94,7 @@ namespace BlackMisc
             case CAircraftSituation::OnGroundByGuessing: return intGuess;
             case CAircraftSituation::OnGroundByInterpolation: return intInter;
             case CAircraftSituation::OutOnGroundOwnAircraft: return outOwnAircraft;
-            case CAircraftSituation::InFromNetworkSituation: return inNetwork;
+            case CAircraftSituation::InFromNetwork: return inNetwork;
             case CAircraftSituation::InFromParts: return inFromParts;
             case CAircraftSituation::InNoGroundInfo: return InNoGroundInfo;
             case CAircraftSituation::NotSet:
@@ -122,7 +120,7 @@ namespace BlackMisc
             case IndexPitch: return m_pitch.propertyByIndex(index.copyFrontRemoved());
             case IndexBank: return m_bank.propertyByIndex(index.copyFrontRemoved());
             case IndexGroundSpeed: return m_groundSpeed.propertyByIndex(index.copyFrontRemoved());
-            case IndexGroundElevation: return m_groundElevation.propertyByIndex(index.copyFrontRemoved());
+            case IndexGroundElevationPlane: return m_groundElevationPlane.propertyByIndex(index.copyFrontRemoved());
             case IndexCallsign: return m_correspondingCallsign.propertyByIndex(index.copyFrontRemoved());
             case IndexIsOnGround: return CVariant::fromValue(m_isOnGround);
             case IndexIsOnGroundString: return CVariant::fromValue(this->isOnGroundAsString());
@@ -144,7 +142,7 @@ namespace BlackMisc
             case IndexPitch: m_pitch.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
             case IndexBank: m_bank.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
             case IndexGroundSpeed: m_groundSpeed.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
-            case IndexGroundElevation: m_groundElevation.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
+            case IndexGroundElevationPlane: m_groundElevationPlane.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
             case IndexCallsign: m_correspondingCallsign.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
             case IndexIsOnGround: m_isOnGround = variant.toInt(); break;
             case IndexOnGroundReliability: m_onGroundDetails = variant.toInt(); break;
@@ -164,7 +162,7 @@ namespace BlackMisc
             case IndexPitch: return m_pitch.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getPitch());
             case IndexBank: return m_bank.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getBank());
             case IndexGroundSpeed: return m_groundSpeed.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getGroundSpeed());
-            case IndexGroundElevation: return m_groundElevation.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getGroundElevation());
+            case IndexGroundElevationPlane: return m_groundElevationPlane.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getGroundElevationPlane());
             case IndexCallsign: return m_correspondingCallsign.comparePropertyByIndex(index.copyFrontRemoved(), compareValue.getCallsign());
             case IndexIsOnGround:
             case IndexIsOnGroundString:
@@ -191,7 +189,7 @@ namespace BlackMisc
             m_heading.setNull();
             m_pitch.setNull();
             m_bank.setNull();
-            m_groundElevation.setNull();
+            m_groundElevationPlane.setNull();
             m_groundSpeed.setNull();
             m_onGroundDetails = CAircraftSituation::NotSet;
         }
@@ -207,10 +205,10 @@ namespace BlackMisc
                    this->getOnGroundDetails() != CAircraftSituation::NotSet;
         }
 
-        void CAircraftSituation::setOnGround(CAircraftSituation::IsOnGround onGround, CAircraftSituation::OnGroundDetails reliability)
+        void CAircraftSituation::setOnGround(CAircraftSituation::IsOnGround onGround, CAircraftSituation::OnGroundDetails details)
         {
             this->setOnGround(onGround);
-            this->setOnGroundReliabiliy(reliability);
+            this->setOnGroundDetails(details);
         }
 
         const QString &CAircraftSituation::getOnDetailsAsString() const
@@ -228,21 +226,44 @@ namespace BlackMisc
             return !this->getGroundElevation().isNull();
         }
 
-        bool CAircraftSituation::setGroundElevationChecked(const CAltitude &elevation, bool ignoreNullValues, bool overrideExisting)
+        bool CAircraftSituation::hasInboundGroundInformation() const
         {
-            if (ignoreNullValues && elevation.isNull()) { return false; }
-            if (!overrideExisting && this->hasGroundElevation()) { return false; }
-            m_groundElevation = elevation;
-            return true;
+            return this->getOnGroundDetails() == CAircraftSituation::InFromParts || this->getOnGroundDetails() == CAircraftSituation::InFromNetwork;
         }
 
-        bool CAircraftSituation::setGroundElevationChecked(const CElevationPlane &elevationPlane, bool ignoreNullValues, bool overrideExisting)
+        void CAircraftSituation::setGroundElevation(const CAltitude &altitude)
         {
-            if (ignoreNullValues && elevationPlane.isNull()) { return false; }
-            if (!overrideExisting && this->hasGroundElevation()) { return false; }
-            if (!elevationPlane.isWithinRange(*this)) { return false; }
-            m_groundElevation = elevationPlane.getAltitude();
-            return true;
+            if (altitude.isNull())
+            {
+                m_groundElevationPlane = CElevationPlane::null();
+            }
+            else
+            {
+                m_groundElevationPlane = CElevationPlane(*this);
+                m_groundElevationPlane.setSinglePointRadius();
+                m_groundElevationPlane.setGeodeticHeight(altitude);
+            }
+        }
+
+        bool CAircraftSituation::setGroundElevationChecked(const CElevationPlane &elevationPlane)
+        {
+            if (elevationPlane.isNull()) { return false; }
+            const CLength distance =  this->calculateGreatCircleDistance(elevationPlane);
+            if (distance > elevationPlane.getRadius()) { return false; }
+            if (m_groundElevationPlane.isNull() || distance < m_groundElevationPlane.getRadius())
+            {
+                // better values
+                m_groundElevationPlane = elevationPlane;
+                m_groundElevationPlane.setRadius(distance);
+                return true;
+            }
+            return false;
+        }
+
+        const CLength &CAircraftSituation::getGroundElevationDistance() const
+        {
+            if (!this->hasGroundElevation()) { return CLength::null(); }
+            return m_groundElevationPlane.getRadius();
         }
 
         CLength CAircraftSituation::getHeightAboveGround() const
@@ -258,29 +279,31 @@ namespace BlackMisc
             return this->getAltitude() - gh;
         }
 
-        CAltitude CAircraftSituation::getCorrectedAltitude(const CLength &centerOfGravity, bool *corrected) const
+        CAltitude CAircraftSituation::getCorrectedAltitude(const CLength &centerOfGravity, bool dragToGround, bool *corrected) const
         {
             if (corrected) { *corrected = false; }
-            if (this->getGroundElevation().isNull()) { return this->getAltitude(); }
+            if (!this->hasGroundElevation()) { return this->getAltitude(); }
 
             // above ground
             if (this->getAltitude().getReferenceDatum() == CAltitude::AboveGround)
             {
-                const CAltitude aboveGround = this->getAltitude().withOffset(centerOfGravity);
-                const bool c = !aboveGround.isPositiveWithEpsilonConsidered();
-                if (corrected) { *corrected = c; }
-                return c ?
-                       CAltitude(0, CAltitude::AboveGround, aboveGround.getUnit()) :
-                       aboveGround;
+                BLACK_VERIFY_X(false, Q_FUNC_INFO, "Unsupported");
+                return this->getAltitude();
             }
             else
             {
+                static const CLength small(0.5, CLengthUnit::m());
                 const CAltitude groundPlusCG = this->getGroundElevation().withOffset(centerOfGravity);
-                const bool c = (this->getAltitude() < groundPlusCG);
-                if (corrected) { *corrected = c; }
-                return c ?
-                       groundPlusCG :
-                       this->getAltitude();
+                const CLength groundDistance = (this->getAltitude() - groundPlusCG);
+                if (groundDistance.abs() < small) { return this->getAltitude(); }
+                const bool toGround = (this->getAltitude() < groundPlusCG) || (forceToGround && this->isOnGround() == OnGround);
+                if (toGround)
+                {
+                    // underflow or overflow forced to ground
+                    if (corrected) { *corrected = true; }
+                    return groundPlusCG;
+                }
+                return this->getAltitude();
             }
         }
 
@@ -311,5 +334,50 @@ namespace BlackMisc
             m_correspondingCallsign = callsign;
             m_correspondingCallsign.setTypeHint(CCallsign::Aircraft);
         }
+
+        bool CAircraftSituation::adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor, qint64 *differenceMs)
+        {
+            Q_ASSERT_X(timeDeviationFactor >= 0 && timeDeviationFactor <= 1.0, Q_FUNC_INFO, "Expect 0..1");
+            static const qint64 Max = std::numeric_limits<qint64>::max();
+            if (differenceMs) { *differenceMs = Max; }
+            if (this->getOnGroundDetails() == CAircraftSituation::InFromNetwork) { return false; }
+            const qint64 d = this->getAdjustedTimeDifferenceMs(parts.getAdjustedMSecsSinceEpoch());
+            const bool adjust = (d >= 0) || qAbs(d) < (timeDeviationFactor * parts.getTimeOffsetMs()); // future or past within deviation range
+            if (!adjust) { return false; }
+
+            if (differenceMs) { *differenceMs = d; }
+            this->setOnGround(parts.isOnGround() ? CAircraftSituation::OnGround : CAircraftSituation::NotOnGround, CAircraftSituation::InFromParts);
+            return true;
+        }
+
+        bool CAircraftSituation::adjustGroundFlag(const CAircraftPartsList &partsList, double timeDeviationFactor, qint64 *differenceMs)
+        {
+            Q_ASSERT_X(timeDeviationFactor >= 0 && timeDeviationFactor <= 1.0, Q_FUNC_INFO, "Expect 0..1");
+            if (this->getOnGroundDetails() == CAircraftSituation::InFromNetwork) { return false; }
+            if (partsList.isEmpty()) { return false; }
+
+            static const qint64 Max = std::numeric_limits<qint64>::max();
+            if (differenceMs) { *differenceMs = Max; }
+            CAircraftParts bestParts;
+            bool adjust = false;
+            qint64 bestDistance = Max;
+            for (const CAircraftParts &parts : partsList)
+            {
+                const qint64 d = this->getAdjustedTimeDifferenceMs(parts.getAdjustedMSecsSinceEpoch());
+                const qint64 posD = qAbs(d);
+                const bool candidate = (d >= 0) || posD < (timeDeviationFactor * parts.getTimeOffsetMs()); // future or past within deviation range
+                if (!candidate || bestDistance <= posD) { continue; }
+                bestDistance = posD;
+                if (differenceMs) { *differenceMs = d; }
+                adjust = true;
+                bestParts = parts;
+                if (bestDistance == 0) { break; }
+            }
+            if (!adjust) { return false; }
+
+            const CAircraftSituation::IsOnGround og = bestParts.isOnGround() ? CAircraftSituation::OnGround : CAircraftSituation::NotOnGround;
+            this->setOnGround(og, CAircraftSituation::InFromParts);
+            return true;
+        }
     } // namespace
 } // namespace
diff --git a/src/blackmisc/aviation/aircraftsituation.h b/src/blackmisc/aviation/aircraftsituation.h
index 3ef780375..62d3c8520 100644
--- a/src/blackmisc/aviation/aircraftsituation.h
+++ b/src/blackmisc/aviation/aircraftsituation.h
@@ -16,6 +16,7 @@
 #include "blackmisc/aviation/callsign.h"
 #include "blackmisc/aviation/heading.h"
 #include "blackmisc/blackmiscexport.h"
+#include "blackmisc/geo/elevationplane.h"
 #include "blackmisc/geo/coordinategeodetic.h"
 #include "blackmisc/geo/latitude.h"
 #include "blackmisc/geo/longitude.h"
@@ -39,6 +40,9 @@ namespace BlackMisc
     namespace Geo { class CElevationPlane; }
     namespace Aviation
     {
+        class CAircraftParts;
+        class CAircraftPartsList;
+
         //! Value object encapsulating information of an aircraft's situation
         class BLACKMISC_EXPORT CAircraftSituation :
             public CValueObject<CAircraftSituation>,
@@ -60,7 +64,7 @@ namespace BlackMisc
                 IndexOnGroundReliabilityString,
                 IndexPitch,
                 IndexGroundSpeed,
-                IndexGroundElevation,
+                IndexGroundElevationPlane,
                 IndexCallsign
             };
 
@@ -82,9 +86,9 @@ namespace BlackMisc
                 OnGroundByElevation,
                 OnGroundByGuessing,       //!< weakest
                 // received situation
-                InFromNetworkSituation,   //!< received from network
-                InFromParts,
-                InNoGroundInfo,
+                InFromNetwork,            //!< received from network
+                InFromParts,              //!< set from aircraft parts
+                InNoGroundInfo,           //!< not know
                 // send information
                 OutOnGroundOwnAircraft    //!< sending on ground
             };
@@ -101,7 +105,7 @@ namespace BlackMisc
                                const PhysicalQuantities::CAngle &pitch = {},
                                const PhysicalQuantities::CAngle &bank = {},
                                const PhysicalQuantities::CSpeed &gs = {},
-                               const CAltitude &groundElevation = { 0, nullptr });
+                               const Geo::CElevationPlane &groundElevation = {});
 
             //! Comprehensive constructor
             CAircraftSituation(const CCallsign &correspondingCallsign,
@@ -110,7 +114,7 @@ namespace BlackMisc
                                const PhysicalQuantities::CAngle &pitch = {},
                                const PhysicalQuantities::CAngle &bank = {},
                                const PhysicalQuantities::CSpeed &gs = {},
-                               const CAltitude &groundElevation = { 0, nullptr });
+                               const Geo::CElevationPlane &groundElevation = {});
 
             //! \copydoc Mixin::Index::propertyByIndex
             CVariant propertyByIndex(const CPropertyIndex &index) const;
@@ -151,11 +155,14 @@ namespace BlackMisc
             //! On ground info available?
             bool isOnGroundInfoAvailable() const;
 
+            //! Set on ground
+            void setOnGround(bool onGround) { this->setOnGround(onGround ? OnGround : NotOnGround); }
+
             //! Set on ground
             void setOnGround(CAircraftSituation::IsOnGround onGround) { m_isOnGround = static_cast<int>(onGround); }
 
             //! Set on ground
-            void setOnGround(CAircraftSituation::IsOnGround onGround, CAircraftSituation::OnGroundDetails reliability);
+            void setOnGround(CAircraftSituation::IsOnGround onGround, CAircraftSituation::OnGroundDetails details);
 
             //! On ground reliability
             OnGroundDetails getOnGroundDetails() const { return static_cast<CAircraftSituation::OnGroundDetails>(m_onGroundDetails); }
@@ -163,8 +170,8 @@ namespace BlackMisc
             //! On ground reliability as string
             const QString &getOnDetailsAsString() const;
 
-            //! Reliability
-            void setOnGroundReliabiliy(CAircraftSituation::OnGroundDetails onGroundReliability) { m_onGroundDetails = static_cast<int>(onGroundReliability); }
+            //! On ground details
+            void setOnGroundDetails(CAircraftSituation::OnGroundDetails details) { m_onGroundDetails = static_cast<int>(details); }
 
             //! On ground info as string
             QString getOnGroundInfo() const;
@@ -179,19 +186,29 @@ namespace BlackMisc
             virtual std::array<double, 3> normalVectorDouble() const override { return m_position.normalVectorDouble(); }
 
             //! Elevation of the ground directly beneath
-            const CAltitude &getGroundElevation() const { return m_groundElevation; }
+            const CAltitude &getGroundElevation() const { return m_groundElevationPlane.getAltitude(); }
+
+            //! Elevation of the ground directly beneath
+            const Geo::CElevationPlane &getGroundElevationPlane() const { return m_groundElevationPlane; }
 
             //! Is ground elevation value available
             bool hasGroundElevation() const;
 
+            //! Has inbound ground information
+            bool hasInboundGroundInformation() const;
+
+            //! Elevation of the ground directly beneath at the given situation
+            void setGroundElevation(const Aviation::CAltitude &altitude);
+
             //! Elevation of the ground directly beneath
-            void setGroundElevation(const CAltitude &elevation) { m_groundElevation = elevation; }
+            void setGroundElevation(const Geo::CElevationPlane &elevationPlane) { m_groundElevationPlane = elevationPlane; }
 
             //! Set elevation of the ground directly beneath, but checked
-            bool setGroundElevationChecked(const CAltitude &elevation, bool ignoreNullValues = true, bool overrideExisting = true);
+            //! \remark override if better
+            bool setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane);
 
-            //! Set elevation of the ground directly beneath, but checked
-            bool setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane, bool ignoreNullValues = true, bool overrideExisting = true);
+            //! Distance of ground elevation
+            const PhysicalQuantities::CLength &getGroundElevationDistance() const;
 
             //! Height above ground.
             PhysicalQuantities::CLength getHeightAboveGround() const;
@@ -206,7 +223,7 @@ namespace BlackMisc
             const CAltitude &getAltitude() const { return m_position.geodeticHeight(); }
 
             //! Get altitude under consideration of ground elevation
-            CAltitude getCorrectedAltitude(const PhysicalQuantities::CLength &centerOfGravity = {}, bool *corrected = nullptr) const;
+            CAltitude getCorrectedAltitude(const PhysicalQuantities::CLength &centerOfGravity = {}, bool forceToGround = true, bool *corrected = nullptr) const;
 
             //! Set altitude
             void setAltitude(const CAltitude &altitude) { m_position.setGeodeticHeight(altitude); }
@@ -250,6 +267,20 @@ namespace BlackMisc
             //! Set flag indicating this is an interim position update
             void setInterimFlag(bool flag) { m_isInterim = flag; }
 
+            //! Transfer ground flag from parts
+            //! \param parts containing the gnd flag
+            //! \param alwaysSetDetails mark as CAircraftSituation::InFromParts regardless of parts
+            //! \param timeDeviationFactor 0..1 (of offset time) small deviations from time are accepted
+            //! \param differenceMs returns time difference
+            bool adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor = 0.1, qint64 *differenceMs = nullptr);
+
+            //! Transfer ground flag from parts list
+            //! \param partsList containing the gnd flag
+            //! \param alwaysSetDetails mark as CAircraftSituation::InFromParts regardless of parts
+            //! \param timeDeviationFactor 0..1 (of offset time) small deviations from time are accepted
+            //! \param differenceMs returns time difference
+            bool adjustGroundFlag(const CAircraftPartsList &partsList, double timeDeviationFactor = 0.1, qint64 *differenceMs = nullptr);
+
             //! Get flag indicating this is an interim position update
             bool isInterim() const { return m_isInterim; }
 
@@ -270,7 +301,7 @@ namespace BlackMisc
             PhysicalQuantities::CAngle m_pitch;
             PhysicalQuantities::CAngle m_bank;
             PhysicalQuantities::CSpeed m_groundSpeed;
-            CAltitude m_groundElevation{ 0, CAltitude::MeanSeaLevel, PhysicalQuantities::CLengthUnit::nullUnit() };
+            Geo::CElevationPlane m_groundElevationPlane; //!< NULL elevation as default
             int m_isOnGround = static_cast<int>(CAircraftSituation::OnGroundSituationUnknown);
             int m_onGroundDetails = static_cast<int>(CAircraftSituation::NotSet);
             bool m_isInterim = false;
@@ -284,7 +315,7 @@ namespace BlackMisc
                 BLACK_METAMEMBER(pitch),
                 BLACK_METAMEMBER(bank),
                 BLACK_METAMEMBER(groundSpeed),
-                BLACK_METAMEMBER(groundElevation),
+                BLACK_METAMEMBER(groundElevationPlane),
                 BLACK_METAMEMBER(isOnGround),
                 BLACK_METAMEMBER(onGroundDetails),
                 BLACK_METAMEMBER(timestampMSecsSinceEpoch),
diff --git a/src/blackmisc/aviation/aircraftsituationlist.cpp b/src/blackmisc/aviation/aircraftsituationlist.cpp
index c161d1000..aaaa41b78 100644
--- a/src/blackmisc/aviation/aircraftsituationlist.cpp
+++ b/src/blackmisc/aviation/aircraftsituationlist.cpp
@@ -30,29 +30,52 @@ namespace BlackMisc
             CSequence<CAircraftSituation>(il)
         { }
 
-        int CAircraftSituationList::setGroundElevationChecked(const CElevationPlane &elevationPlane, bool ignoreNullValues, bool overrideExisting)
+        int CAircraftSituationList::setGroundElevationChecked(const CElevationPlane &elevationPlane, qint64 newerThanAdjustedMs)
         {
-            if (ignoreNullValues && elevationPlane.isNull()) { return 0; }
+            if (elevationPlane.isNull()) { return 0; }
             int c = 0;
             for (CAircraftSituation &s : *this)
             {
-                const bool set = s.setGroundElevationChecked(elevationPlane, ignoreNullValues, overrideExisting);
+                if (newerThanAdjustedMs >= 0 && s.getAdjustedMSecsSinceEpoch() <= newerThanAdjustedMs) { continue; }
+                const bool set = s.setGroundElevationChecked(elevationPlane);
                 if (set) { c++; }
             }
             return c;
         }
 
-        int CAircraftSituationList::setGroundElevationChecked(const CElevationPlane &elevationPlane, qint64 newerThanAdjustedMs, bool ignoreNullValues, bool overrideExisting)
+        int CAircraftSituationList::adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor)
         {
-            if (ignoreNullValues && elevationPlane.isNull()) { return 0; }
             int c = 0;
-            for (CAircraftSituation &s : *this)
+            for (CAircraftSituation &situation : *this)
             {
-                if (s.getAdjustedMSecsSinceEpoch() <= newerThanAdjustedMs) { continue; }
-                const bool set = s.setGroundElevationChecked(elevationPlane, ignoreNullValues, overrideExisting);
-                if (set) { c++; }
+                if (situation.adjustGroundFlag(parts, timeDeviationFactor)) { c++; };
             }
             return c;
         }
+
+        int CAircraftSituationList::extrapolateGroundFlag()
+        {
+            if (this->isEmpty()) { return 0; }
+            CAircraftSituationList withInfo = this->findByInboundGroundInformation(true);
+            withInfo.sortLatestFirst();
+            if (withInfo.isEmpty()) { return 0; }
+            const CAircraftSituation latest = withInfo.front();
+
+            int c = 0;
+            for (CAircraftSituation &situation : *this)
+            {
+                if (situation.isNewerThanAdjusted(latest))
+                {
+                    situation.setOnGround(latest.isOnGround(), latest.getOnGroundDetails());
+                    c++;
+                }
+            }
+            return c;
+        }
+
+        CAircraftSituationList CAircraftSituationList::findByInboundGroundInformation(bool hasGroundInfo) const
+        {
+            return this->findBy(&CAircraftSituation::hasInboundGroundInformation, hasGroundInfo);
+        }
     } // namespace
 } // namespace
diff --git a/src/blackmisc/aviation/aircraftsituationlist.h b/src/blackmisc/aviation/aircraftsituationlist.h
index 1426db31d..4b20d6453 100644
--- a/src/blackmisc/aviation/aircraftsituationlist.h
+++ b/src/blackmisc/aviation/aircraftsituationlist.h
@@ -14,6 +14,7 @@
 
 #include "blackmisc/aviation/aircraftsituation.h"
 #include "blackmisc/aviation/callsignobjectlist.h"
+#include "blackmisc/geo/geoobjectlist.h"
 #include "blackmisc/geo/elevationplane.h"
 #include "blackmisc/blackmiscexport.h"
 #include "blackmisc/collection.h"
@@ -28,11 +29,12 @@ namespace BlackMisc
     namespace Geo { class CElevationPlane; }
     namespace Aviation
     {
-        class CAircraftSituation;
+        class CAircraftParts;
 
         //! Value object encapsulating a list of aircraft situations
         class BLACKMISC_EXPORT CAircraftSituationList :
             public CSequence<CAircraftSituation>,
+            public Geo::IGeoObjectList<CAircraftSituation, CAircraftSituationList>,
             public ITimestampWithOffsetObjectList<CAircraftSituation, CAircraftSituationList>,
             public ICallsignObjectList<CAircraftSituation, CAircraftSituationList>,
             public Mixin::MetaType<CAircraftSituationList>
@@ -50,10 +52,16 @@ namespace BlackMisc
             CAircraftSituationList(std::initializer_list<CAircraftSituation> il);
 
             //! Set ground elevation from elevation plane
-            int setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane, bool ignoreNullValues = true, bool overrideExisting = true);
+            int setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane, qint64 newerThanAdjustedMs = -1);
 
-            //! Set ground elevation from elevation plane
-            int setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane, qint64 newerThanAdjustedMs, bool ignoreNullValues = true, bool overrideExisting = true);
+            //! Adjust flag by using CAircraftSituation::adjustGroundFlag
+            int adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor = 0.1);
+
+            //! Extrapolate ground flag into the future
+            int extrapolateGroundFlag();
+
+            //! Find if having inbound information
+            CAircraftSituationList findByInboundGroundInformation(bool hasGroundInfo) const;
         };
     } // namespace
 } // namespace
diff --git a/src/blackmisc/geo/elevationplane.cpp b/src/blackmisc/geo/elevationplane.cpp
index d05176f5c..103c4d97c 100644
--- a/src/blackmisc/geo/elevationplane.cpp
+++ b/src/blackmisc/geo/elevationplane.cpp
@@ -89,15 +89,16 @@ namespace BlackMisc
             const ColumnIndex i = index.frontCasted<ColumnIndex>();
             switch (i)
             {
-            case IndexRadius:
-                m_radius.setPropertyByIndex(index.copyFrontRemoved(), variant);
-                break;
-            default:
-                CCoordinateGeodetic::setPropertyByIndex(index, variant);
-                break;
+            case IndexRadius: m_radius.setPropertyByIndex(index.copyFrontRemoved(), variant); break;
+            default: CCoordinateGeodetic::setPropertyByIndex(index, variant); break;
             }
         }
 
+        int CElevationPlane::comparePropertyByIndex(const CPropertyIndex &index, const CElevationPlane &elevationPlane) const
+        {
+            return this->getAltitude().comparePropertyByIndex(index, elevationPlane.getAltitude());
+        }
+
         // 100km/h 27,8m/s
         //  50km/h 13,9m/s
         // 100kts  51,4m/s
@@ -118,5 +119,11 @@ namespace BlackMisc
             static const CLength l(1000.0, CLengthUnit::m());
             return l;
         }
+
+        const CElevationPlane &CElevationPlane::null()
+        {
+            static const CElevationPlane p;
+            return p;
+        }
     } // namespace
 } // namespace
diff --git a/src/blackmisc/geo/elevationplane.h b/src/blackmisc/geo/elevationplane.h
index 2b6a95f33..84441a396 100644
--- a/src/blackmisc/geo/elevationplane.h
+++ b/src/blackmisc/geo/elevationplane.h
@@ -12,14 +12,15 @@
 #ifndef BLACKMISC_GEO_ELEVATIONPLANE_H
 #define BLACKMISC_GEO_ELEVATIONPLANE_H
 
-#include "blackmisc/blackmiscexport.h"
 #include "blackmisc/geo/coordinategeodetic.h"
+#include "blackmisc/blackmiscexport.h"
 
 namespace BlackMisc
 {
     namespace Geo
     {
         //! Plane of same elevation, can be a single point or larger area (e.g. airport)
+        //! \remark 100km/h 1sec => 28m
         class BLACKMISC_EXPORT CElevationPlane :
             public CValueObject<CElevationPlane, CCoordinateGeodetic>
         {
@@ -73,6 +74,9 @@ namespace BlackMisc
             //! \copydoc BlackMisc::Mixin::Index::setPropertyByIndex
             void setPropertyByIndex(const CPropertyIndex &index, const CVariant &variant);
 
+            //! Compare by index
+            int comparePropertyByIndex(const CPropertyIndex &index, const CElevationPlane &elevationPlane) const;
+
             //! \copydoc BlackMisc::Mixin::String::toQString
             QString convertToQString(bool i18n = false) const;
 
@@ -85,6 +89,9 @@ namespace BlackMisc
             //! Radius for major airport
             static const PhysicalQuantities::CLength &majorAirportRadius();
 
+            //! NULL plane
+            static const CElevationPlane &null();
+
         private:
             PhysicalQuantities::CLength m_radius { 0, nullptr }; //!< elevation is valid in radius
 
diff --git a/src/blackmisc/simulation/interpolationhints.cpp b/src/blackmisc/simulation/interpolationhints.cpp
index 64a6b1083..854c90a8f 100644
--- a/src/blackmisc/simulation/interpolationhints.cpp
+++ b/src/blackmisc/simulation/interpolationhints.cpp
@@ -30,10 +30,41 @@ namespace BlackMisc
             m_isVtol(isVtolAircraft), m_hasParts(hasParts), m_logInterpolation(log)
         { }
 
+        const CElevationPlane &CInterpolationHints::getElevationPlane(ICoordinateGeodetic &reference, const CLength &radius, SituationLog *log) const
+        {
+            if (m_elevationPlane.isNull())
+            {
+                if (log)
+                {
+                    static const QString lm("By provider (no valid plane)");
+                    log->elevationInfo = lm;
+                }
+                return CElevationPlane::null();
+            }
+            const CLength d = reference.calculateGreatCircleDistance(m_elevationPlane);
+            if (d <= radius)
+            {
+                if (log)
+                {
+                    static const QString lm("Using elevation plane, distance: %1");
+                    log->elevationInfo = lm.arg(d.valueRoundedWithUnit(CLengthUnit::m(), 1));
+                }
+                return m_elevationPlane;
+            }
+            else
+            {
+                if (log)
+                {
+                    static const QString lm("Invalid elevation plane, distance: %1");
+                    log->elevationInfo = lm.arg(d.valueRoundedWithUnit(CLengthUnit::m(), 1));
+                }
+                return CElevationPlane::null();
+            }
+        }
+
         CAltitude CInterpolationHints::getGroundElevation(const CAircraftSituation &situation, bool useProvider, bool forceProvider, SituationLog *log) const
         {
-            static const CLength null = CLength(0, CLengthUnit::nullUnit());
-            return this->getGroundElevation(situation, null, useProvider, forceProvider, log);
+            return this->getGroundElevation(situation, CLength::null(), useProvider, forceProvider, log);
         }
 
         CAltitude CInterpolationHints::getGroundElevation(const CAircraftSituation &situation, const CLength &validRadius, bool useProvider, bool forceProvider, SituationLog *log) const
@@ -46,6 +77,7 @@ namespace BlackMisc
                     static const QString lm("By provider (forced)");
                     log->elevationInfo = lm;
                 }
+                Q_ASSERT_X(false, Q_FUNC_INFO, "Elevation provider must no longer be used");
                 return m_elevationProvider(situation);
             }
 
@@ -80,6 +112,16 @@ namespace BlackMisc
             return CAltitude::null();
         }
 
+        CAltitude CInterpolationHints::getGroundElevation(const CAircraftSituation &situation, const CLength &validRadius, SituationLog *log) const
+        {
+            return this->getGroundElevation(situation, validRadius, false, false, log);
+        }
+
+        CAltitude CInterpolationHints::getGroundElevation(const CAircraftSituation &situation, SituationLog *log) const
+        {
+            return this->getGroundElevation(situation, CLength::null(), log);
+        }
+
         void CInterpolationHints::resetElevationPlane()
         {
             m_elevationPlane = CElevationPlane();
@@ -87,7 +129,7 @@ namespace BlackMisc
 
         bool CInterpolationHints::isWithinRange(const Geo::ICoordinateGeodetic &coordinate) const
         {
-            if (m_elevationPlane.isNull()) return false;
+            if (m_elevationPlane.isNull()) { return false; }
             return m_elevationPlane.isWithinRange(coordinate);
         }
 
diff --git a/src/blackmisc/simulation/interpolationhints.h b/src/blackmisc/simulation/interpolationhints.h
index 6166dc0c2..52131aeee 100644
--- a/src/blackmisc/simulation/interpolationhints.h
+++ b/src/blackmisc/simulation/interpolationhints.h
@@ -48,6 +48,9 @@ namespace BlackMisc
             //! Get elevation plane
             const Geo::CElevationPlane &getElevationPlane() const { return m_elevationPlane;}
 
+            //! Get elevation plane
+            const Geo::CElevationPlane &getElevationPlane(Geo::ICoordinateGeodetic &reference, const PhysicalQuantities::CLength &radius, SituationLog *log = nullptr) const;
+
             //! Set elevation
             //! \remark used to store a ground elevation and use it as well for nearby situatons
             void setElevationPlane(const Geo::CElevationPlane &elevation) { m_elevationPlane = elevation; }
@@ -55,6 +58,8 @@ namespace BlackMisc
             //! Elevation plane set to null
             void resetElevationPlane();
 
+        private:
+            //! \todo KB 2018-03 ground flag refactoring
             //! Get elevation from CInterpolationHints::getElevationProvider or CInterpolationHints::getElevation
             //! \remark avoid unnecessary calls on XPlane (calling elevation provider)
             //! \param situation where to check
@@ -63,12 +68,23 @@ namespace BlackMisc
             //! \param log optional chance to write info about elevation
             //! \see setElevationProvider
             //! \see setElevationPlane
+            //! \deprecated
             Aviation::CAltitude getGroundElevation(const Aviation::CAircraftSituation &situation, bool useProvider, bool forceProvider = false, SituationLog *log = nullptr) const;
 
             //! Get elevation from CInterpolationHints::getElevationProvider or CInterpolationHints::getElevation
             //! \remark if validRadius is >= Geo::CElevationPlane::radius use validRadius
+            //! \deprecated
             Aviation::CAltitude getGroundElevation(const Aviation::CAircraftSituation &situation, const PhysicalQuantities::CLength &validRadius, bool useProvider, bool forceProvider = false, SituationLog *log = nullptr) const;
 
+            //! Get ground elevation by using the elevation plane
+            //! \deprecated
+            Aviation::CAltitude getGroundElevation(const Aviation::CAircraftSituation &situation, const PhysicalQuantities::CLength &validRadius, SituationLog *log = nullptr) const;
+
+            //! Get ground elevation by using the elevation plane
+            //! \deprecated
+            Aviation::CAltitude getGroundElevation(const Aviation::CAircraftSituation &situation, SituationLog *log = nullptr) const;
+
+        public:
             //! Check if elevation is within radius and can be used
             bool isWithinRange(const Geo::ICoordinateGeodetic &coordinate) const;
 
@@ -110,12 +126,14 @@ namespace BlackMisc
             using ElevationProvider = std::function<Aviation::CAltitude(const Aviation::CAircraftSituation &)>;
 
             //! Has elevation provider?
+            //! \deprecated
             bool hasElevationProvider() const;
 
             //! Set function object that can obtain ground elevation
             //! \remark either a provider can be used or an elevation plan can be set
             //! \see setElevationPlane
             //! \see getGroundElevation
+            //! \deprecated
             void setElevationProvider(const ElevationProvider &ep) { m_elevationProvider = ep; }
 
             //! \copydoc BlackMisc::Mixin::Index::propertyByIndex
diff --git a/src/blackmisc/simulation/interpolator.cpp b/src/blackmisc/simulation/interpolator.cpp
index 5b117ba65..f2bc3376e 100644
--- a/src/blackmisc/simulation/interpolator.cpp
+++ b/src/blackmisc/simulation/interpolator.cpp
@@ -74,12 +74,14 @@ namespace BlackMisc
                 currentSituation.setCallsign(m_callsign);
             }
 
+            //! \todo KB 2018-03 ground flag refactoring
             // Update current position by hints' elevation
             // * for XP provided by hints.getElevationProvider at current position
             // * for FSX/P3D provided as hints.getElevation which is set to current position of remote aircraft in simulator
             // * As XP uses lazy init we will call getGroundElevation only when needed
             // * default here via getElevationPlane
-            CAltitude currentGroundElevation(hints.getGroundElevation(currentSituation, currentSituation.getDistancePerTime(1000), true, false, logP));
+            // CAltitude currentGroundElevation(hints.getGroundElevation(currentSituation, currentSituation.getDistancePerTime(1000), true, false, logP));
+            const CElevationPlane currentGroundElevation = hints.getElevationPlane(currentSituation, currentSituation.getDistancePerTime(1000), logP);
             currentSituation.setGroundElevation(currentGroundElevation); // set as default
 
             // data, split situations by time
@@ -410,15 +412,6 @@ namespace BlackMisc
             return IRemoteAircraftProvider::MaxSituationsPerCallsign;
         }
 
-        template <typename Derived>
-        void CInterpolator<Derived>::setGroundElevationFromHint(const CInterpolationHints &hints, CAircraftSituation &situation, bool override)
-        {
-            if (!override && situation.hasGroundElevation()) { return; }
-            const CAltitude elevation = hints.getGroundElevation(situation, false);
-            if (elevation.isNull()) { return; }
-            situation.setGroundElevation(elevation);
-        }
-
         template <typename Derived>
         void CInterpolator<Derived>::setGroundFlagFromInterpolator(const CInterpolationHints &hints, double groundFactor, CAircraftSituation &situation)
         {
diff --git a/src/blackmisc/simulation/interpolator.h b/src/blackmisc/simulation/interpolator.h
index 8beac9c47..e6f02e0e1 100644
--- a/src/blackmisc/simulation/interpolator.h
+++ b/src/blackmisc/simulation/interpolator.h
@@ -112,9 +112,6 @@ namespace BlackMisc
             //! Constructor
             CInterpolator(const QString &objectName, const Aviation::CCallsign &callsign, QObject *parent);
 
-            //! Set the ground elevation from hints
-            static void setGroundElevationFromHint(const CInterpolationHints &hints, Aviation::CAircraftSituation &situation, bool override = true);
-
             //! Set on ground flag
             static void setGroundFlagFromInterpolator(const CInterpolationHints &hints, double groundFactor, Aviation::CAircraftSituation &situation);
 
diff --git a/src/blackmisc/simulation/interpolatorlinear.cpp b/src/blackmisc/simulation/interpolatorlinear.cpp
index f2075f932..1b9f6bd5c 100644
--- a/src/blackmisc/simulation/interpolatorlinear.cpp
+++ b/src/blackmisc/simulation/interpolatorlinear.cpp
@@ -120,8 +120,8 @@ namespace BlackMisc
             // do not call for XP (lazy init)
             if (!hints.hasElevationProvider())
             {
-                CInterpolator::setGroundElevationFromHint(hints, oldSituation, false);
-                CInterpolator::setGroundElevationFromHint(hints, newSituation, false);
+                oldSituation.setGroundElevationChecked(hints.getElevationPlane());
+                newSituation.setGroundElevationChecked(hints.getElevationPlane());
             }
 
             CAircraftSituation currentSituation(oldSituation); // also sets ground elevation if available
diff --git a/src/blackmisc/simulation/simulatedaircraft.h b/src/blackmisc/simulation/simulatedaircraft.h
index 61e588e45..894abb4bb 100644
--- a/src/blackmisc/simulation/simulatedaircraft.h
+++ b/src/blackmisc/simulation/simulatedaircraft.h
@@ -213,7 +213,10 @@ namespace BlackMisc
             const BlackMisc::Aviation::CAltitude &getGroundElevation() const { return m_situation.getGroundElevation(); }
 
             //! \copydoc BlackMisc::Aviation::CAircraftSituation::setGroundElevation
-            void setGroundElevation(const BlackMisc::Aviation::CAltitude &elevation) { m_situation.setGroundElevation(elevation); }
+            void setGroundElevation(const Geo::CElevationPlane &elevation) { m_situation.setGroundElevation(elevation); }
+
+            //! \copydoc BlackMisc::Aviation::CAircraftSituation::setGroundElevation
+            void setGroundElevationChecked(const Geo::CElevationPlane &elevation) { m_situation.setGroundElevationChecked(elevation); }
 
             //! \copydoc BlackMisc::Aviation::CAircraftSituation::getHeading
             const BlackMisc::Aviation::CHeading &getHeading() const { return m_situation.getHeading(); }
diff --git a/src/blackmisc/simulation/simulatedaircraftlist.cpp b/src/blackmisc/simulation/simulatedaircraftlist.cpp
index b8815e267..c509ee5c9 100644
--- a/src/blackmisc/simulation/simulatedaircraftlist.cpp
+++ b/src/blackmisc/simulation/simulatedaircraftlist.cpp
@@ -20,8 +20,8 @@
 #include <QString>
 #include <tuple>
 
-using namespace BlackMisc;
 using namespace BlackMisc::Aviation;
+using namespace BlackMisc::Geo;
 using namespace BlackMisc::PhysicalQuantities;
 using namespace BlackMisc::Network;
 
@@ -160,13 +160,13 @@ namespace BlackMisc
             return c;
         }
 
-        int CSimulatedAircraftList::setGroundElevation(const CCallsign &callsign, const CAltitude &elevation, bool onlyFirst)
+        int CSimulatedAircraftList::setGroundElevationChecked(const CCallsign &callsign, const CElevationPlane &elevation, bool onlyFirst)
         {
             int c = 0;
             for (CSimulatedAircraft &aircraft : (*this))
             {
                 if (aircraft.getCallsign() != callsign) { continue; }
-                aircraft.setGroundElevation(elevation);
+                aircraft.setGroundElevationChecked(elevation);
                 c++;
                 if (onlyFirst) break;
             }
@@ -227,7 +227,7 @@ namespace BlackMisc
             return c;
         }
 
-        int CSimulatedAircraftList::countAircraftPartsSyncronized() const
+        int CSimulatedAircraftList::countAircraftPartsSynchronized() const
         {
             int c = 0;
             for (const CSimulatedAircraft &aircraft : (*this))
diff --git a/src/blackmisc/simulation/simulatedaircraftlist.h b/src/blackmisc/simulation/simulatedaircraftlist.h
index 098c13491..4a3eb0268 100644
--- a/src/blackmisc/simulation/simulatedaircraftlist.h
+++ b/src/blackmisc/simulation/simulatedaircraftlist.h
@@ -12,16 +12,15 @@
 #ifndef BLACKMISC_SIMULATION_SIMULATEDNAIRCRAFTLIST_H
 #define BLACKMISC_SIMULATION_SIMULATEDNAIRCRAFTLIST_H
 
+#include "blackmisc/simulation/simulatedaircraft.h"
 #include "blackmisc/aviation/callsignobjectlist.h"
 #include "blackmisc/aviation/callsignset.h"
-#include "blackmisc/blackmiscexport.h"
-#include "blackmisc/collection.h"
 #include "blackmisc/geo/geoobjectlist.h"
 #include "blackmisc/network/userlist.h"
+#include "blackmisc/blackmiscexport.h"
+#include "blackmisc/collection.h"
 #include "blackmisc/sequence.h"
-#include "blackmisc/simulation/simulatedaircraft.h"
 #include "blackmisc/variant.h"
-
 #include <QMetaType>
 
 namespace BlackMisc
@@ -92,7 +91,7 @@ namespace BlackMisc
             int setAircraftSituation(const Aviation::CCallsign &callsign, const Aviation::CAircraftSituation &situation, bool onlyFirst = true);
 
             //! Set ground elevation
-            int setGroundElevation(const Aviation::CCallsign &callsign, const Aviation::CAltitude &elevation, bool onlyFirst = true);
+            int setGroundElevationChecked(const Aviation::CCallsign &callsign, const Geo::CElevationPlane &elevation, bool onlyFirst = true);
 
             //! Enabled?
             bool isEnabled(const Aviation::CCallsign &callsign) const;
@@ -110,7 +109,7 @@ namespace BlackMisc
             int countRendered() const;
 
             //! Number of aircraft with parts
-            int countAircraftPartsSyncronized() const;
+            int countAircraftPartsSynchronized() const;
         };
     } //namespace
 } // namespace
diff --git a/tests/blackmisc/testinterpolatorlinear.cpp b/tests/blackmisc/testinterpolatorlinear.cpp
index fbd3805c7..ca07d029b 100644
--- a/tests/blackmisc/testinterpolatorlinear.cpp
+++ b/tests/blackmisc/testinterpolatorlinear.cpp
@@ -165,7 +165,8 @@ namespace BlackMiscTest
         const CSpeed gs(number * 10, CSpeedUnit::km_h());
         const CAltitude gndElev({ 0, CLengthUnit::m() }, CAltitude::MeanSeaLevel);
         const CCoordinateGeodetic c(lat, lng, alt);
-        CAircraftSituation s(callsign, c, heading, pitch, bank, gs, gndElev);
+        CAircraftSituation s(callsign, c, heading, pitch, bank, gs);
+        s.setGroundElevation(gndElev);
         s.setMSecsSinceEpoch(ts - deltaT * number); // values in past
         s.setTimeOffsetMs(offset);
         return s;