Registration deed vs resurvey sketch

Hi Sir/ Madam. My father has a property in his name with registered deed executed in 1987. Later on he was of out of india for works. During 1993 a resurvey came in the area and the boundaries / sketch was drawn in such a way that the area assigned in the registered deed was not fully covered in the govt sketch. This was unaware to us we were not in india. Recently he has come to india in 2003 and he has settled here since then. Now due to some land disputes we have requested for re-survey from Taluk level. The resurvey based on our application was done and officer mentioned that registeration deed is of no value and what is mentioned in the govt. sketch is final. My dad has been paying tax for the entire area as mentioned in the registration deed but actually the area is not there. Please adivise what is to be done here.