Analytical models ofthermal imaging system performance have gradually become obsolete as thermal imaging systems (TIS) have become more complex and have improved in vertical performance. In particular, the effects of sampling and aliasing have not been included directly, but have had to be accounted for by side calculations before entering the data. An approach to modeling second-generation TIS is described in which the effects of sampling on both signal and noise are accounted for without requiring the user to make subsidiary calculations. Proper treatment of the several sources of noise in sampled systems is analyzed, including aliased noise. The model is two dimensional, using both vertical and horizontal resolution in the prediction of recognition and detection performance. A model for human perception is presented that differs slightly from matched filter models.