Land Surveying Legal Question

After 20 years, I’m studying civil engineering like my Daddy wanted. This semester I am taking two classes in surveying. This past week, I asked a question that wasn’t answered to my satisfaction. I verified that when a licensed surveyor makes a plat, ALL of his notes are considered legal documents. My teacher elaborated that these are the only legal documents allowed to be made in pencil. He also said that entries were not allowed to be erased. If a correction or change is made it is struck out and initialed, the entry must remain legible. This is people’s property we are talking about, so I understand the need for this. A surveyor working with a transit and notebook can do this, but what about a surveyor working with a GPS unit and electronic data collector? Is there electronic media that cannot be altered without leaving a trace? It must have the condition of being portable and cost effective.