A thermal imager detects relative differences in surface temperature, and these differences are converted into an electronic signal and shown as a visual image on a display for the user to observe. Modern thermal imagers can detect even small differences in surface temperature. The Law Enforcement Thermographers' Association has recognized 12 uses for thermal imaging in law enforcement: search and rescue operations, environmental investigations, officer safety, fugitive searches, disturbed surface investigations, structure profiles, marine and ground surveillance, perimeter surveillance, accident/collision investigation, vehicle profiles, and hidden compartments. Before LETA recognizes an application for thermal imaging, the technology must first be successfully used in that manner, and it must then survive a court challenge regarding the appropriateness of the use of thermal imaging in a given context. The aforementioned uses of thermal imaging are approved uses for land-based thermal imagers. Handheld and vehicle-mounted thermal imagers are similar in their base construction and function. One of the most common options on thermal imagers allows for recording and remote viewing of the video signal. Some models have video output connections, and others have wireless transmitters that use radio frequency or microwave signals.