Telescopic mast. A convenient method of elevating a camera to take 'low-altitude' aerial photographs. A series of aluminium sections of different diametres, which, when retracted, are stored within each other. When the mast is extended (by compressed air), the camera can be elevated to about 20 - 25 metres (65 - 80 feet) or even higher, where it is operated remotely. The higher masts are usually installed semi-permanently on a 4 x 4 or other suitable vehicle or sometimes mounted on trailers. Shorter masts can be hand-carried and stabilised with a tripod.