Synthetic images are used for a variety of applications, from computer games to military training and testing of sensor systems. SensorVision TM from MultiGen-Paradigm Incorporated is a commercial software for the generation of synthetic infrared (IR) images in real-time. The Swedish Defence Research Agency (FOI) has performed an initial validation of this software. In this report, the radiometric accuracy of SensorVision has been investigated in the long wave infrared region, 8-12 Micrometers. The validation was performed through a comparison of data generated by SensorVision and data measured on Swedish terrain. The comparison consists of an examination of the mean values and the standard deviations of specific areas in the images. Comparing the mean values, it was found that the deviation from measured values in the selected areas were 3-7.5 %. These differences are caused by a number of processes that need to be considered in order to obtain as accurate results as possible. Also, a theoretical analysis of some of the approximations in the equations used by SensorVision was made. In this analysis, it was seen that significant errors were introduced due to SensorVision approximations. If these are acceptable or not is dependent on the application.