This Technical Report defines procedures for the determination of errors, appropriate corrections and the evaluation of measurement uncertainty contributors due to thermal influences in the performance of length measurements for geometrical product specification (GPS), when— the mean temperature is the standard reference temperature,— the mean temperature is not the standard reference temperature and where the mean is taken over time and space,— temperature varies with time.Three cases are considered:a) the mean temperature is the standard reference temperature;b) the mean temperature is not the standard reference temperature and the user makes corrections;c) the mean temperature is not the standard reference temperature and the user makes no corrections.This Technical Report provides the specialized details for the analysis of thermal influence when broader analyses, such as those in accordance with ISO/TS 14253-2, show that thermal effects are significant contributors to the measurement uncertainty, systematic error or both. While temperature gradients are not covered in detail, some information is given (see Annex A).