Ultrasonic NDE and inspection techniques are often strongly influenced by procedures and human factors as well as the underlying physics of the measurement technique. Automation of some of the acquisition tasks potentially eliminates some sources of error. The NDE group at Imperial College London has developed permanently installed ultrasonic thickness monitoring tools which allow frequent acquisition as well as automatic evaluation of ultrasonic wall thickness estimates. Several thousand sensors have been deployed in field and some of the outcomes from site data will be presented. The factors that influence the automated systemÕs performance will be discussed in this paper with a view to giving an indication of the different aspects that are important when trying to evaluate thickness measurements as a function of time. The automated thickness measurements are then compared to measurements that are collected with manually collected measurements using the conventional inspection approach.