diff --git a/EyeRecToo/src/data/DataTuple.h b/EyeRecToo/src/data/DataTuple.h
index f48f2673811955f584a3d343d01b959842f56fd4..88fe16955d5999e7d6943c9c981240cbc2259d81 100644
--- a/EyeRecToo/src/data/DataTuple.h
+++ b/EyeRecToo/src/data/DataTuple.h
@@ -35,11 +35,6 @@ public:
     cv::Mat gazeEstimationVisualization;
     bool showGazeEstimationVisualization;
 
-    static const QString TIMESTAMP;
-    static const QString LEFT_EYE_PREFIX;
-    static const QString RIGHT_EYE_PREFIX;
-    static const QString FIELD_PREFIX;
-
     static QString header()
     {
         return journalField(TIMESTAMP) % FieldData().header(FIELD_PREFIX) % EyeData().header(LEFT_EYE_PREFIX) % EyeData().header(RIGHT_EYE_PREFIX);
@@ -48,6 +43,12 @@ public:
     {
         return journalField(timestamp) % field.toQString() % lEye.toQString() % rEye.toQString();
     }
+
+private:
+    static const QString TIMESTAMP;
+    static const QString LEFT_EYE_PREFIX;
+    static const QString RIGHT_EYE_PREFIX;
+    static const QString FIELD_PREFIX;
 };
 
 #endif // DATATUPLE_H
diff --git a/EyeRecToo/src/data/EyeData.h b/EyeRecToo/src/data/EyeData.h
index 104721da90551152ff8b44e117663018d1cf3538..acc2c1754162a0cdaa2a16188a91013801d2b42f 100644
--- a/EyeRecToo/src/data/EyeData.h
+++ b/EyeRecToo/src/data/EyeData.h
@@ -54,26 +54,6 @@ public:
     cv::Rect coarseROI;
     std::shared_ptr<CameraCalibration> cameraCalibration;
 
-    static const QString TIMESTAMP;
-    static const QString PUPIL_X;
-    static const QString PUPIL_Y;
-    static const QString PUPIL_WIDTH;
-    static const QString PUPIL_HEIGHT;
-    static const QString PUPIL_ANGLE;
-    static const QString PUPIL_CONFIDENCE;
-    static const QString GAZE_X;
-    static const QString GAZE_Y;
-    static const QString GAZE_Z;
-    static const QString INSTANTANEOUS_GAZE_X;
-    static const QString INSTANTANEOUS_GAZE_Y;
-    static const QString INSTANTANEOUS_GAZE_Z;
-    static const QString EYE_X;
-    static const QString EYE_Y;
-    static const QString EYE_Z;
-    static const QString EYE_CONFIDENCE;
-    static const QString VALID;
-    static const QString PROCESSING_TIME;
-
     // TODO: header, toQString, and the reading from file (see the Calibration class) should be unified
     // to avoid placing things in the wrong order / with the wrong string
     QString header(QString prefix = "") const override
@@ -122,6 +102,26 @@ private:
         str.append(journalField(validPupil));
         str.append(journalField(processingTimestamp));
     }
+
+    static const QString TIMESTAMP;
+    static const QString PUPIL_X;
+    static const QString PUPIL_Y;
+    static const QString PUPIL_WIDTH;
+    static const QString PUPIL_HEIGHT;
+    static const QString PUPIL_ANGLE;
+    static const QString PUPIL_CONFIDENCE;
+    static const QString GAZE_X;
+    static const QString GAZE_Y;
+    static const QString GAZE_Z;
+    static const QString INSTANTANEOUS_GAZE_X;
+    static const QString INSTANTANEOUS_GAZE_Y;
+    static const QString INSTANTANEOUS_GAZE_Z;
+    static const QString EYE_X;
+    static const QString EYE_Y;
+    static const QString EYE_Z;
+    static const QString EYE_CONFIDENCE;
+    static const QString VALID;
+    static const QString PROCESSING_TIME;
 };
 Q_DECLARE_METATYPE(EyeData)
 
diff --git a/EyeRecToo/src/data/FieldData.h b/EyeRecToo/src/data/FieldData.h
index 445b91d7291a7b598a1ede285b96c1b0ce7d9fc2..991f48426bbad4603b7386f4cff3aa96f0323f9e 100644
--- a/EyeRecToo/src/data/FieldData.h
+++ b/EyeRecToo/src/data/FieldData.h
@@ -51,22 +51,6 @@ public:
     unsigned int height;
     std::shared_ptr<CameraCalibration> cameraCalibration;
 
-    static const QString TIMESTAMP;
-    static const QString GAZE_X;
-    static const QString GAZE_Y;
-    static const QString GAZE_CONFIDENCE;
-    static const QString GAZE_VALID;
-    static const QString GAZE_META;
-    static const QString CM_ID;
-    static const QString CM_X;
-    static const QString CM_Y;
-    static const QString CM_Z;
-    static const QString UNDISTORTED;
-    static const QString WIDTH;
-    static const QString HEIGHT;
-    static const QString MARKERS;
-    static const QString PROCESSING_TIME;
-
     QString header(QString prefix = "") const override
     {
         return prefix % journalField(TIMESTAMP)
@@ -107,6 +91,22 @@ private:
         str.append(Token::Delimiter);
         str.append(journalField(processingTimestamp));
     }
+
+    static const QString TIMESTAMP;
+    static const QString GAZE_X;
+    static const QString GAZE_Y;
+    static const QString GAZE_CONFIDENCE;
+    static const QString GAZE_VALID;
+    static const QString GAZE_META;
+    static const QString CM_ID;
+    static const QString CM_X;
+    static const QString CM_Y;
+    static const QString CM_Z;
+    static const QString UNDISTORTED;
+    static const QString WIDTH;
+    static const QString HEIGHT;
+    static const QString MARKERS;
+    static const QString PROCESSING_TIME;
 };
 Q_DECLARE_METATYPE(FieldData)