ARTOA4-UserManual/Offsets.md

 **column Offset Start Date (non editable)**
 
-taken from soso file. Gives date on which Offset Start was determined
+taken from "-offset" in  soso file. Gives date on which Offset Start was determined
 
 **column Offset Start (non editable)**
 
-taken from soso file. Gives SoSo offset on Offset Start Date (negative = late?)
+taken from "-offset" in soso file. Gives SoSo offset on Offset Start Date (negative = late?)
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+
+**column Offset End Date (non editable)**
+
+taken from "-rcv_offset" in soso file. Gives date on which Offset End was determined
+
+**column Offset End (non editable)**
+
+taken from "-rcv_offset" in soso file. Gives SoSo offset on Offset End Date (negative = late?)
+
+**column Drift (non editable), \[seconds/day)**
+
+taken from "-drift" in soso file.  Manually calculated by editor of soso file as: 
+
+(Offset_End - Offset_Start) / (Offset_End_Date - Offset_Start_Date)
+
+**column Measured SoundSpeed (non editable)**
+
+calculated by"Sound_Speed_Method" on basis of average temperature of selected temperatures (in window "Edit-Temperature")
+
+**column Empirical SoundSpeed (non editable)**
+
+taken from "-sound_speed" in soso file.  (Note to programmer: Should be changed to "-empiric_sound_speed for consistency of nomencalture)
+
+**column Optimum SoundSpeed (non editable)**
+
+calculated by ARTOA "Calculate offsets"  How????
+
+**column Applied SoundSpeed (editable !)**
+
+value set by either copying "Measured", "Emprical" or " Optimum" to "Applied" (see window "Offset controls", lower right) or by manually typing into this field. 
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