diff --git a/include/animation.h b/include/animation.h
index b4d3cccb4505803a2a37df093ccbda512fc6e189..6713dbf54c01e1e72ef45bfec12c12a37760746f 100644
--- a/include/animation.h
+++ b/include/animation.h
@@ -114,25 +114,25 @@ public:
     int getNumFrames(); 
 
     // Returns the maximum number of frames in the source file
-    int getMaxFrames();
+    int getMaxFrames() const;
  
     // Returns the index of the current frame  
-    int getCurrentFrameNum();
+    int getCurrentFrameNum() const;
 
     // Sets the sourceIn/Out frame numbers
     void updateSourceInFrameNum(int in=-1);
     void updateSourceOutFrameNum(int out=-1);
 
     // Returns the sourceIn/Out frame numbers
-    int getSourceInFrameNum();
-    int getSourceOutFrameNum();
+    int getSourceInFrameNum() const;
+    int getSourceOutFrameNum() const;
  
     // Returns the filename of the current frame  
     QString getCurrentFileName();
  
     // Returns the FPS of the current animation if it is a video
     double getFPS();
-    double getOriginalFPS();
+    double getOriginalFPS() const;
 
     void setFPS(double fps);
  
@@ -144,17 +144,17 @@ public:
 
     void reset();
  
-    bool isVideo();
-    bool isStereoVideo();
-    bool isImageSequence();
-    bool isCameraLiveStream();
+    bool isVideo() const;
+    bool isStereoVideo() const;
+    bool isImageSequence() const;
+    bool isCameraLiveStream() const;
 
 #ifndef STEREO_DISABLED
     enum Camera getCamera();
     void setCamera(enum Camera);
 #endif
-    int getFirstFrameSec();
-    int getFirstFrameMicroSec();
+    int getFirstFrameSec() const;
+    int getFirstFrameMicroSec() const;
 
     QString getFileBase();
     QFileInfo getFileInfo();
diff --git a/include/aviFileWriter.h b/include/aviFileWriter.h
index a8d6cf45e959214c2f7cf1eff01f118be728e2c0..131ddd07d0d6566bc0d5fb0be19f52e8a3d133b4 100644
--- a/include/aviFileWriter.h
+++ b/include/aviFileWriter.h
@@ -92,7 +92,7 @@ public:
       double  iFramerate );
 
    /** Get the the bytes written */
-   long int bytesWritten();
+   long int bytesWritten() const;
 
    /**
     * Load a bitmap from a file and append it to the current open .avi.
diff --git a/include/backgroundFilter.h b/include/backgroundFilter.h
index fc0144344e6484f8111e685eb92d9a20654bc0c2..39055eef6c9e93cd5f27411f7a3e3b4d91500a77 100644
--- a/include/backgroundFilter.h
+++ b/include/backgroundFilter.h
@@ -52,7 +52,7 @@ public:
     void setDefaultHeight(double h);
 
     void setUpdate(bool b);
-    bool update();
+    bool update() const;
 
     QString getFilename();
     void setFilename(const QString &fn);
diff --git a/include/control.h b/include/control.h
index c310d7ac86128b6414f7569327ab2e1456fe42f5..4155485dc69b93779c32f8d9481ca29a83e301b2 100644
--- a/include/control.h
+++ b/include/control.h
@@ -192,7 +192,7 @@ public:
     int getCalibGrid3DResolution();
     void setCalibGrid3DResolution(int i);
 
-    void expandRange(QColor& fromColor, QColor& toColor, const QColor& clickedColor);
+    void expandRange(QColor& fromColor, QColor& toColor, const QColor& clickedColor) const;
     void saveChange(const QColor& fromColor, const QColor& toColor, RectPlotItem* map);
     bool getColors(QColor& clickedColor, QColor& toColor, QColor& fromColor, RectPlotItem*& map);
 
diff --git a/include/coordItem.h b/include/coordItem.h
index ca21934ee9e995fecb0e2a111eefb71368ec4c2b..26707f7192045882bd0741711edc021cca88a0ef 100644
--- a/include/coordItem.h
+++ b/include/coordItem.h
@@ -49,7 +49,7 @@ public:
     {
         this->coordDimension = dim;
     }
-    inline int /*Dimension*/ getCoordDimension()
+    inline int /*Dimension*/ getCoordDimension() const
     {
         return this->coordDimension;
     }
diff --git a/include/extrCalibration.h b/include/extrCalibration.h
index 6e3b988e4d997752959ee7bb0213a07678f370f7..9efb8197381ac1a63a5b817c1b264e7c1f563f23 100644
--- a/include/extrCalibration.h
+++ b/include/extrCalibration.h
@@ -186,7 +186,7 @@ public:
     {
         this->points2D = list2D;
     }
-    inline float getCamHeight()
+    inline float getCamHeight() const
     {
         return camHeight;
     }
diff --git a/include/filter.h b/include/filter.h
index 70093b8159a18bdf1e4b0a7bf2d0ee8f67c26541..23b3a7297eec717f7f9dd925e375997fdeb12c86 100644
--- a/include/filter.h
+++ b/include/filter.h
@@ -49,17 +49,17 @@ public:
     void setFilter(Filter *filter);
     Filter * getFilter();
 
-    double value();
-    double getValue();
+    double value() const;
+    double getValue() const;
     void setValue(double d);
 
-    double getMinimum();
+    double getMinimum() const;
     void setMinimum(double d);
-    double getMaximum();
+    double getMaximum() const;
     void setMaximum(double d);
 
-    bool changed();
-    bool getChanged();
+    bool changed() const;
+    bool getChanged() const;
     void setChanged(bool b);
 };
 
@@ -93,7 +93,7 @@ public:
     Filter();
     virtual ~Filter() {};
 
-    bool changed();
+    bool changed() const;
     bool getChanged();
     void setChanged(bool b);
 
@@ -110,10 +110,10 @@ public:
     void enable();
     void disable();
     void setEnabled(bool b);
-    bool getEnabled();
+    bool getEnabled() const;
 
     void setOnCopy(bool b);
-    bool getOnCopy();
+    bool getOnCopy() const;
 };
 
 #endif
diff --git a/include/gridItem.h b/include/gridItem.h
index 350c9140cd9502ed26c8b5eee6019a2e06a4326a..fcba1d5c481c40102e67097d647cd36cf40145c9 100644
--- a/include/gridItem.h
+++ b/include/gridItem.h
@@ -41,7 +41,7 @@ public:
     {
         this->gridDimension = gDimension;
     }
-    inline int/*Petrack::Dimension*/ getGridDimension()
+    inline int/*Petrack::Dimension*/ getGridDimension() const
     {
         return this->gridDimension;
     }
diff --git a/include/logoItem.h b/include/logoItem.h
index 686fc01c3beed579e0d2a97678cd6c40287bbe57..ac8aaeff0bb4d23f1b26899947d93e4030df8cc0 100644
--- a/include/logoItem.h
+++ b/include/logoItem.h
@@ -52,7 +52,7 @@ public:
 //    void dropEvent(QDropEvent *event);
 
     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
-    inline float getOpacity()
+    inline float getOpacity() const
     {
         return mOpacity;
     }
diff --git a/include/petrack.h b/include/petrack.h
index e8351780a7896ee52d72469fdc49d40688b3d68e..5ef7a3d8f764429c85a3eefa06ce5d8930941d94 100644
--- a/include/petrack.h
+++ b/include/petrack.h
@@ -180,13 +180,13 @@ public:
     void updateSequence();
 //    void calcBackground();
     QSet<int> getOnlyVisible();
-    double getCmPerPixel();
+    double getCmPerPixel() const;
     void setHeadSize(double hS=-1);
     double getHeadSize(QPointF *pos=nullptr, int pers=-1, int frame=-1);
 
     //------------------------------
     // inline function
-    bool isLoading()
+    bool isLoading() const
     {
         return mLoading;
     }
@@ -349,7 +349,7 @@ public:
     {
         mRecognitionChanged = b;
     }
-    inline bool recognitionChanged()
+    inline bool recognitionChanged() const
     {
         return mRecognitionChanged;
     }
@@ -358,7 +358,7 @@ public:
     {
         mTrackChanged = b;
     }
-    inline bool trackChanged()
+    inline bool trackChanged() const
     {
         return mTrackChanged;
     }
@@ -426,7 +426,7 @@ public:
     {
         return &mExtrCalibration;
     }
-    inline double getStatusFPS()
+    inline double getStatusFPS() const
     {
         return mShowFPS;
     }
diff --git a/include/player.h b/include/player.h
index 56045cabb0e2dfbf2bfa652b85929b55b6fcdfbd..c3e3e5c64048a97038503b73d33439294d169ad9 100644
--- a/include/player.h
+++ b/include/player.h
@@ -81,7 +81,7 @@ public slots:
     void setFPS(double fps=-1.);
     void togglePlayerSpeedLimited();
     void setPlayerSpeedLimited(bool fixed);
-    bool getPlayerSpeedLimited();
+    bool getPlayerSpeedLimited() const;
     void setPlayerSpeedFixed(bool fixed);
     void setLooping(bool looping);
     void setFrameInNum(int in=-1.);
diff --git a/include/stereoContext.h b/include/stereoContext.h
index 4064b453fff178d1dd110e8f7c0087c8404b03a5..b89f0fe6b57f504b7d8d1985b8db24429986ced6 100644
--- a/include/stereoContext.h
+++ b/include/stereoContext.h
@@ -97,20 +97,20 @@ public:
         return mTriclopsContext;
     }
 #endif
-    inline unsigned char getSurfaceValue()
+    inline unsigned char getSurfaceValue() const
     {
         return mSurfaceValue;
     }
-    inline unsigned char getBackForthValue()
+    inline unsigned char getBackForthValue() const
     {
         return mBackForthValue;
     }
 
-    inline unsigned short int getMin()
+    inline unsigned short int getMin() const
     {
         return mMin;
     }
-    inline unsigned short int getMax()
+    inline unsigned short int getMax() const
     {
         return mMax;
     }
diff --git a/src/animation.cpp b/src/animation.cpp
index 24fab6940f4015c30a97ea8e3c5c232a830133ba..cdb5d6091f07da27b9a7ac3ff20e050bc816828d 100644
--- a/src/animation.cpp
+++ b/src/animation.cpp
@@ -255,11 +255,11 @@ bool Animation::openTimeFile(QString &timeFileName)
 }
 
 /// returns -1, if not set by time file
-int Animation::getFirstFrameSec()
+int Animation::getFirstFrameSec() const
 {
     return mFirstSec;
 }
-int Animation::getFirstFrameMicroSec()
+int Animation::getFirstFrameMicroSec() const
 {
     return mFirstMicroSec;
 }
@@ -368,7 +368,7 @@ int Animation::getNumFrames()
     return 0;
 }
 
-int Animation::getMaxFrames()
+int Animation::getMaxFrames() const
 {
     if (mVideo || mImgSeq)
         return mMaxFrames;
@@ -376,7 +376,7 @@ int Animation::getMaxFrames()
 }
 
 /// Returns the index of the current frame
-int Animation::getCurrentFrameNum()
+int Animation::getCurrentFrameNum() const
 {
     return mCurrentFrame;
 }
@@ -391,7 +391,7 @@ void Animation::setSourceInFrameNum(int in)
     mMainWindow->updateSourceInOutFrames();
 }
 /// Returns the sourceIn frame number
-int Animation::getSourceInFrameNum()
+int Animation::getSourceInFrameNum() const
 {
     return mSourceInFrame;
 }
@@ -406,7 +406,7 @@ void Animation::setSourceOutFrameNum(int out)
     mMainWindow->updateSourceInOutFrames();
 }
 /// Returns the sourceOut frame number
-int Animation::getSourceOutFrameNum()
+int Animation::getSourceOutFrameNum() const
 {
     return mSourceOutFrame;
 }
@@ -449,7 +449,7 @@ double Animation::getFPS()
         return -1;
 }
 
-double Animation::getOriginalFPS()
+double Animation::getOriginalFPS() const
 {
     return mOriginalFps;
 }
@@ -532,22 +532,22 @@ QFileInfo Animation::getFileInfo()
     return mFileInfo;
 }
 
-bool Animation::isVideo()
+bool Animation::isVideo() const
 {
     return mVideo;
 }
 
-bool Animation::isStereoVideo()
+bool Animation::isStereoVideo() const
 {
     return mStereo;
 }
 
-bool Animation::isImageSequence()
+bool Animation::isImageSequence() const
 {
     return mImgSeq;
 }
 
-bool Animation::isCameraLiveStream()
+bool Animation::isCameraLiveStream() const
 {
     return mCameraLiveStream;
 }
diff --git a/src/aviFileWriter.cpp b/src/aviFileWriter.cpp
index ff5c5fed22a221c4405466f0ddc87d16c3c1a357..f981e7e27dd8bf654e0fce7b77467b5261b1c919 100644
--- a/src/aviFileWriter.cpp
+++ b/src/aviFileWriter.cpp
@@ -265,7 +265,7 @@ bool AviFileWriter::open(
   //return m_vWriter.open(pszFilename,CV_FOURCC('P', 'I', 'M', '1'),(double) iFramerate,Size(iCols,iRows),m_isColor);
 }
 
-long int AviFileWriter::bytesWritten()
+long int AviFileWriter::bytesWritten() const
 {
    return m_liBytesWritten;
    //return m_iTimeIndex * m_iSize;
diff --git a/src/backgroundFilter.cpp b/src/backgroundFilter.cpp
index 2d5456c6deeaa97a94777388824d01ea20156146..21723d6dcb16685faa8a2ea30c92157949daad10 100644
--- a/src/backgroundFilter.cpp
+++ b/src/backgroundFilter.cpp
@@ -327,7 +327,7 @@ void BackgroundFilter::setUpdate(bool b)
     mUpdate = b;
 }
 
-bool BackgroundFilter::update()
+bool BackgroundFilter::update() const
 {
     return mUpdate;
 }
diff --git a/src/control.cpp b/src/control.cpp
index 20cd72dcbc3f738098f86d1da3c862666677559b..768e8d208dc9541bbeeeb6d2b0f44293baa63445 100644
--- a/src/control.cpp
+++ b/src/control.cpp
@@ -3520,7 +3520,7 @@ void Control::saveChange(const QColor& fromColor, const QColor& toColor, RectPlo
  * @param toColor[in,out] toColor of the map, gets changed!
  * @param clickedColor[in]
  */
-void Control::expandRange(QColor& fromColor, QColor& toColor, const QColor& clickedColor)
+void Control::expandRange(QColor& fromColor, QColor& toColor, const QColor& clickedColor) const
 {
     // NOTE BUFFER in Klassenebene verschieben und bei setColor auch nutzen? (verschiedene Größe vllt. gewünscht?)
     constexpr int BUFFER = 10;
diff --git a/src/filter.cpp b/src/filter.cpp
index 1d69d1f21b72d7d2cdc8bee4cdfc2fb5dc2ebb18..dca46edbbf6fa5c9eef40e586ea200e9dd46fb2c 100644
--- a/src/filter.cpp
+++ b/src/filter.cpp
@@ -39,11 +39,11 @@ Filter * Parameter::getFilter()
     return mFilter;
 }
 
-double Parameter::value()
+double Parameter::value() const
 {
     return mValue;
 }
-double Parameter::getValue()
+double Parameter::getValue() const
 {
     return mValue;
 }
@@ -56,7 +56,7 @@ void Parameter::setValue(double d)
     }
 }
 
-double Parameter::getMinimum()
+double Parameter::getMinimum() const
 {
     return mMinimum;
 }
@@ -64,7 +64,7 @@ void Parameter::setMinimum(double d)
 {
     mMinimum = d;
 }
-double Parameter::getMaximum()
+double Parameter::getMaximum() const
 {
     return mMaximum;
 }
@@ -73,11 +73,11 @@ void Parameter::setMaximum(double d)
     mMaximum = d;
 }
 
-bool Parameter::changed()
+bool Parameter::changed() const
 {
     return mChg;
 }
-bool Parameter::getChanged()
+bool Parameter::getChanged() const
 {
     return mChg;
 }
@@ -110,7 +110,7 @@ Filter::Filter()
  *
  * @return true, if a parameter changed
  */
-bool Filter::changed()
+bool Filter::changed() const
 {
     return mChg;
 }
@@ -184,7 +184,7 @@ void Filter::setEnabled(bool b)
     mChg = true;
     mEnable = b;
 }
-bool Filter::getEnabled()
+bool Filter::getEnabled() const
 {
     return mEnable;
 }
@@ -194,7 +194,7 @@ void Filter::setOnCopy(bool b)
     mChg = true;
     mOnCopy = b;
 }
-bool Filter::getOnCopy()
+bool Filter::getOnCopy() const
 {
     return mOnCopy;
 }
diff --git a/src/petrack.cpp b/src/petrack.cpp
index 4e768fd4a0197c716fe35ac0f955aecae631e839..2d160a428c8cbc86752a723c90fc8f9cf2e2893e 100644
--- a/src/petrack.cpp
+++ b/src/petrack.cpp
@@ -3959,7 +3959,7 @@ void Petrack::updateSequence()
  * @brief Gets cm per pixel. Only recalculates when calculating head size.
  * @return cm per pixel
  */
-double Petrack::getCmPerPixel()
+double Petrack::getCmPerPixel() const
 {
     return mCmPerPixel;
 }
diff --git a/src/player.cpp b/src/player.cpp
index 1dc3397bef3f70fea31e327736295080ec42a1c7..cf35bcd0e53e232b735955e779437ae7c48d5e32 100644
--- a/src/player.cpp
+++ b/src/player.cpp
@@ -202,7 +202,7 @@ void Player::togglePlayerSpeedLimited()
 {
     setPlayerSpeedLimited(!mPlayerSpeedLimited);
 }
-bool Player::getPlayerSpeedLimited()
+bool Player::getPlayerSpeedLimited() const
 {
     return mPlayerSpeedLimited;
 }