diff --git a/src/blackmisc/aviation/aircraftsituation.cpp b/src/blackmisc/aviation/aircraftsituation.cpp
index fa3e087d2..e2feae4d1 100644
--- a/src/blackmisc/aviation/aircraftsituation.cpp
+++ b/src/blackmisc/aviation/aircraftsituation.cpp
@@ -510,10 +510,16 @@ namespace BlackMisc
             {
                 m_groundElevationPlane = CElevationPlane(*this);
                 m_groundElevationPlane.setSinglePointRadius();
-                m_groundElevationPlane.setGeodeticHeight(altitude);
+                m_groundElevationPlane.setGeodeticHeight(altitude.switchedUnit(this->getAltitudeUnit()));
             }
         }
 
+        void CAircraftSituation::setGroundElevation(const CElevationPlane &elevationPlane)
+        {
+            m_groundElevationPlane = elevationPlane;
+            m_groundElevationPlane.switchUnit(this->getAltitudeOrDefaultUnit()); // we use ft as internal unit, no "must" but simplification
+        }
+
         bool CAircraftSituation::setGroundElevationChecked(const CElevationPlane &elevationPlane)
         {
             if (elevationPlane.isNull()) { return false; }
@@ -522,7 +528,7 @@ namespace BlackMisc
             if (m_groundElevationPlane.isNull() || distance < m_groundElevationPlane.getRadius())
             {
                 // better values
-                m_groundElevationPlane = elevationPlane;
+                this->setGroundElevation(elevationPlane);
                 m_groundElevationPlane.setRadius(distance);
                 return true;
             }
@@ -548,6 +554,12 @@ namespace BlackMisc
             return this->getAltitude() - gh;
         }
 
+        const CLengthUnit &CAircraftSituation::getAltitudeOrDefaultUnit() const
+        {
+            if (this->getAltitude().isNull()) { return CAltitude::defaultUnit(); }
+            return m_position.geodeticHeight().getUnit();
+        }
+
         CAltitude CAircraftSituation::getCorrectedAltitude(bool enableDragToGround, CAircraftSituation::AltitudeCorrection *correction) const
         {
             return this->getCorrectedAltitude(m_cg, enableDragToGround, correction);
@@ -571,7 +583,7 @@ namespace BlackMisc
             }
             else
             {
-                const CAltitude groundPlusCG = this->getGroundElevation().withOffset(centerOfGravity);
+                const CAltitude groundPlusCG = this->getGroundElevation().withOffset(centerOfGravity).switchedUnit(this->getAltitudeOrDefaultUnit());
                 if (groundPlusCG.isNull())
                 {
                     if (correction) { *correction = NoElevation; }
@@ -615,6 +627,11 @@ namespace BlackMisc
             return altCor;
         }
 
+        void CAircraftSituation::setAltitude(const CAltitude &altitude)
+        {
+            m_position.setGeodeticHeight(altitude.switchedUnit(CAltitude::defaultUnit()));
+        }
+
         CAltitude CAircraftSituation::addAltitudeOffset(const CLength &offset)
         {
             if (offset.isNull()) { return this->getAltitude(); }
@@ -675,6 +692,11 @@ namespace BlackMisc
             m_correspondingCallsign.setTypeHint(CCallsign::Aircraft);
         }
 
+        void CAircraftSituation::setCG(const CLength &cg)
+        {
+            m_cg = cg.switchedUnit(this->getAltitudeOrDefaultUnit());
+        }
+
         bool CAircraftSituation::adjustGroundFlag(const CAircraftParts &parts, bool alwaysSetDetails, double timeDeviationFactor, qint64 *differenceMs)
         {
             Q_ASSERT_X(timeDeviationFactor >= 0 && timeDeviationFactor <= 1.0, Q_FUNC_INFO, "Expect 0..1");
diff --git a/src/blackmisc/aviation/aircraftsituation.h b/src/blackmisc/aviation/aircraftsituation.h
index bd154de0d..defaeb683 100644
--- a/src/blackmisc/aviation/aircraftsituation.h
+++ b/src/blackmisc/aviation/aircraftsituation.h
@@ -253,7 +253,7 @@ namespace BlackMisc
             void setGroundElevation(const Aviation::CAltitude &altitude);
 
             //! Elevation of the ground directly beneath
-            void setGroundElevation(const Geo::CElevationPlane &elevationPlane) { m_groundElevationPlane = elevationPlane; }
+            void setGroundElevation(const Geo::CElevationPlane &elevationPlane);
 
             //! Set elevation of the ground directly beneath, but checked
             //! \remark override if better
@@ -277,6 +277,9 @@ namespace BlackMisc
             //! Get altitude unit
             const PhysicalQuantities::CLengthUnit &getAltitudeUnit() const { return m_position.geodeticHeight().getUnit(); }
 
+            //! Get altitude unit
+            const PhysicalQuantities::CLengthUnit &getAltitudeOrDefaultUnit() const;
+
             //! Get altitude under consideration of ground elevation and ground flag
             //! \remark with dragToGround it will also compensate overflows, otherwise only underflow
             //! @{
@@ -291,7 +294,7 @@ namespace BlackMisc
             //! @}
 
             //! Set altitude
-            void setAltitude(const CAltitude &altitude) { m_position.setGeodeticHeight(altitude); }
+            void setAltitude(const CAltitude &altitude);
 
             //! Add offset to altitude
             CAltitude addAltitudeOffset(const PhysicalQuantities::CLength &offset);
@@ -342,7 +345,7 @@ namespace BlackMisc
             const PhysicalQuantities::CLength &getCG() const { return m_cg; }
 
             //! Set CG
-            void setCG(const PhysicalQuantities::CLength &cg) { m_cg = cg; }
+            void setCG(const PhysicalQuantities::CLength &cg);
 
             //! Has CG set?
             bool hasCG() const { return !m_cg.isNull(); }
diff --git a/src/blackmisc/aviation/altitude.cpp b/src/blackmisc/aviation/altitude.cpp
index 39501d12d..42ee415e7 100644
--- a/src/blackmisc/aviation/altitude.cpp
+++ b/src/blackmisc/aviation/altitude.cpp
@@ -16,6 +16,7 @@
 
 #include <Qt>
 #include <QtGlobal>
+#include <QStringBuilder>
 
 using namespace BlackMisc::PhysicalQuantities;
 
@@ -34,7 +35,7 @@ namespace BlackMisc
             CAltitude copy(*this);
             if (!offset.isNull() && !offset.isZeroEpsilonConsidered())
             {
-                copy += offset;
+                copy += offset.switchedUnit(this->getUnit());
             }
             return copy;
         }
@@ -44,6 +45,21 @@ namespace BlackMisc
             *this = this->withOffset(offset);
         }
 
+        CAltitude &CAltitude::switchUnit(const CLengthUnit &newUnit)
+        {
+            if (newUnit.isNull() || this->getUnit().isNull() || this->getUnit() == newUnit) { return *this; }
+            CLength::switchUnit(newUnit);
+            return *this;
+        }
+
+        CAltitude CAltitude::switchedUnit(const CLengthUnit &newUnit) const
+        {
+            if (newUnit.isNull() || this->getUnit().isNull() || this->getUnit() == newUnit) { return *this; }
+            CAltitude copy(*this);
+            copy.switchUnit(newUnit);
+            return copy;
+        }
+
         QString CAltitude::convertToQString(bool i18n) const
         {
             if (this->m_datum == FlightLevel)
@@ -324,6 +340,11 @@ namespace BlackMisc
             return null;
         }
 
+        const CLengthUnit &CAltitude::defaultUnit()
+        {
+            return CLengthUnit::ft();
+        }
+
         const CPressure &CAltitude::standardISASeaLevelPressure()
         {
             // Average sea-level pressure is 1013.25mbar or 1013.25hPa
diff --git a/src/blackmisc/aviation/altitude.h b/src/blackmisc/aviation/altitude.h
index 987c9476c..42891b964 100644
--- a/src/blackmisc/aviation/altitude.h
+++ b/src/blackmisc/aviation/altitude.h
@@ -108,6 +108,12 @@ namespace BlackMisc
             //! Add offset value
             void addOffset(const CLength &offset);
 
+            //! Value in switched unit
+            CAltitude &switchUnit(const PhysicalQuantities::CLengthUnit &newUnit);
+
+            //! Value in switched unit
+            CAltitude switchedUnit(const PhysicalQuantities::CLengthUnit &newUnit) const;
+
             //! AGL Above ground level?
             bool isAboveGroundLevel() const { return AboveGround == this->m_datum; }
 
@@ -176,6 +182,10 @@ namespace BlackMisc
             //! Null altitude (MSL)
             static const CAltitude &null();
 
+            //! Default unit for calculations
+            //! \remark using this is optional and will simplify debugging and calculations
+            static const PhysicalQuantities::CLengthUnit &defaultUnit();
+
             //! Standard pressure 1013.25mbar/hPa
             static const PhysicalQuantities::CPressure &standardISASeaLevelPressure();
 
diff --git a/src/blackmisc/geo/elevationplane.cpp b/src/blackmisc/geo/elevationplane.cpp
index d7be56d41..714885dc2 100644
--- a/src/blackmisc/geo/elevationplane.cpp
+++ b/src/blackmisc/geo/elevationplane.cpp
@@ -45,6 +45,13 @@ namespace BlackMisc
             this->setGeodeticHeight(newAlt);
         }
 
+        void CElevationPlane::switchAltitudeUnit(const CLengthUnit &unit)
+        {
+            if (unit.isNull() || this->getAltitudeUnit().isNull()) { return; }
+            if (this->getAltitudeUnit() == unit) { return; }
+            this->setGeodeticHeight(this->getAltitude().switchedUnit(unit));
+        }
+
         const CAltitude &CElevationPlane::getAltitudeIfWithinRadius(const ICoordinateGeodetic &coordinate) const
         {
             return (isWithinRange(coordinate)) ? geodeticHeight() : CAltitude::null();
diff --git a/src/blackmisc/geo/elevationplane.h b/src/blackmisc/geo/elevationplane.h
index bfbf9d323..ba0e32a04 100644
--- a/src/blackmisc/geo/elevationplane.h
+++ b/src/blackmisc/geo/elevationplane.h
@@ -51,12 +51,18 @@ namespace BlackMisc
             //! Add offset to altitude
             void addAltitudeOffset(const PhysicalQuantities::CLength &offset);
 
+            //! Switch altitude unit
+            void switchAltitudeUnit(const PhysicalQuantities::CLengthUnit &unit);
+
             //! Altitude when within radius, else null
             const Aviation::CAltitude &getAltitudeIfWithinRadius(const ICoordinateGeodetic &coordinate) const;
 
             //! Altitude (synonym for geodetic height)
             const Aviation::CAltitude &getAltitude() const { return this->geodeticHeight(); }
 
+            //! Altitude (synonym for geodetic height) unit
+            const PhysicalQuantities::CLengthUnit &getAltitudeUnit() const { return this->geodeticHeight().getUnit(); }
+
             //! Altitude (synonym for geodetic height)
             Aviation::CAltitude getAltitudeInUnit(const PhysicalQuantities::CLengthUnit &unit) const;
 
diff --git a/src/blackmisc/pq/physicalquantity.cpp b/src/blackmisc/pq/physicalquantity.cpp
index 0740214f8..436d06b87 100644
--- a/src/blackmisc/pq/physicalquantity.cpp
+++ b/src/blackmisc/pq/physicalquantity.cpp
@@ -247,16 +247,23 @@ namespace BlackMisc
         }
 
         template <class MU, class PQ>
-        PQ &CPhysicalQuantity<MU, PQ>::switchUnit(MU newUnit)
+        PQ &CPhysicalQuantity<MU, PQ>::switchUnit(const MU &newUnit)
         {
-            if (m_unit != newUnit)
-            {
-                m_value = newUnit.convertFrom(m_value, m_unit);
-                m_unit = newUnit;
-            }
+            if (m_unit == newUnit || this->isNull()) { return *derived(); }
+            m_value = newUnit.convertFrom(m_value, m_unit);
+            m_unit = newUnit;
             return *derived();
         }
 
+        template <class MU, class PQ>
+        PQ CPhysicalQuantity<MU, PQ>::switchedUnit(const MU &newUnit) const
+        {
+            if (m_unit == newUnit || this->isNull()) { return *derived(); }
+            PQ copy(*derived());
+            copy.switchUnit(newUnit);
+            return copy;
+        }
+
         template <class MU, class PQ>
         bool CPhysicalQuantity<MU, PQ>::isNull() const
         {
@@ -293,7 +300,7 @@ namespace BlackMisc
         }
 
         template <class MU, class PQ>
-        QString CPhysicalQuantity<MU, PQ>::valueRoundedWithUnit(MU unit, int digits, bool i18n) const
+        QString CPhysicalQuantity<MU, PQ>::valueRoundedWithUnit(const MU &unit, int digits, bool i18n) const
         {
             Q_ASSERT_X(!unit.isNull(), Q_FUNC_INFO, "Cannot convert to null");
             if (this->isNull()) { return this->convertToQString(i18n); }
diff --git a/src/blackmisc/pq/physicalquantity.h b/src/blackmisc/pq/physicalquantity.h
index 6614ddab0..8ed95af18 100644
--- a/src/blackmisc/pq/physicalquantity.h
+++ b/src/blackmisc/pq/physicalquantity.h
@@ -74,7 +74,7 @@ namespace BlackMisc
 
             //! Simply set unit, do no calclulate conversion
             //! \sa switchUnit
-            void setUnit(MU unit) { m_unit = unit; }
+            void setUnit(const MU &unit) { m_unit = unit; }
 
             //! Set unit by string
             void setUnitBySymbol(const QString &unitName);
@@ -83,7 +83,10 @@ namespace BlackMisc
             QString getUnitSymbol() const;
 
             //! Change unit, and convert value to maintain the same quantity
-            PQ &switchUnit(MU newUnit);
+            PQ &switchUnit(const MU &newUnit);
+
+            //! Return copy with switched unit
+            PQ switchedUnit(const MU &newUnit) const;
 
             //! Is quantity null?
             bool isNull() const;
@@ -119,7 +122,7 @@ namespace BlackMisc
 
             //! Value to QString with the given unit, e.g. "5.00m"
             //! \note default digits is CMeasurementUnit::getDisplayDigits
-            QString valueRoundedWithUnit(MU unit, int digits = -1, bool i18n = false) const;
+            QString valueRoundedWithUnit(const MU &unit, int digits = -1, bool i18n = false) const;
 
             //! Value to QString with the current unit, e.g. "5.00m"
             //! \note default digits is CMeasurementUnit::getDisplayDigits
@@ -219,24 +222,24 @@ namespace BlackMisc
             //! \copydoc BlackMisc::Mixin::JsonByMetaClass::convertFromJson
             void convertFromJson(const QJsonObject &json);
 
+            //! \copydoc BlackMisc::Mixin::Index::propertyByIndex
+            CVariant propertyByIndex(const CPropertyIndex &index) const;
+
+            //! \copydoc BlackMisc::Mixin::Index::setPropertyByIndex
+            void setPropertyByIndex(const CPropertyIndex &index, const CVariant &variant);
+
+            //! \copydoc BlackMisc::Mixin::String::toQString
+            QString convertToQString(bool i18n = false) const;
+
             //! Parse to string, with specified separator
             void parseFromString(const QString &value, CPqString::SeparatorMode mode);
 
             //! Parse value from string
             void parseFromString(const QString &value);
 
-            //! \copydoc BlackMisc::Mixin::Index::propertyByIndex
-            CVariant propertyByIndex(const BlackMisc::CPropertyIndex &index) const;
-
-            //! \copydoc BlackMisc::Mixin::Index::setPropertyByIndex
-            void setPropertyByIndex(const BlackMisc::CPropertyIndex &index, const CVariant &variant);
-
             //! Compare
             int comparePropertyByIndex(const CPropertyIndex &index, const PQ &pq) const;
 
-            //! \copydoc BlackMisc::Mixin::String::toQString
-            QString convertToQString(bool i18n = false) const;
-
             //! Maximum of 2 quantities
             static const PQ &maxValue(const PQ &pq1, const PQ &pq2);
 
@@ -281,8 +284,7 @@ namespace BlackMisc
         extern template class BLACKMISC_EXPORT_DECLARE_TEMPLATE CPhysicalQuantity<CTimeUnit, CTime>;
         extern template class BLACKMISC_EXPORT_DECLARE_TEMPLATE CPhysicalQuantity<CAccelerationUnit, CAcceleration>;
         //! \endcond
-
-    }
-}
+    } // ns
+} // ns
 
 #endif // guard