Which of the following is a common method used to detect UXO?

Magnetic surveys are a common method used to detect unexploded ordnance (UXO) due to the metallic components within munitions. These surveys utilize magnetometers to measure variations in the Earth's magnetic field caused by metal objects buried in the ground. When a UXO is present, it creates a localized magnetic anomaly that can be detected and mapped by the equipment. This method is effective for detecting a wide variety of UXO types, including bombs, shells, and landmines, and is often employed when areas may not be safe for personnel to conduct manual searches.

In contrast, visual inspection relies on the ability to see the ordnance, which may not be practical in many cases where UXO is buried or camouflaged by the environment. Geological studies focus on the physical characteristics of the terrain and may provide useful context for UXO surveys but are not direct detection methods. Thermal imaging detects heat signatures, which can be useful for certain applications but is generally not effective for locating UXO, especially when the ordnance has been in the ground for extended periods and cooled to ambient temperature.