If you are looking to review and measure irregularities in rails at typical line speeds, the High Speed Rail Corrugation Analyser, or HSRCA, from RailMeasurement allows for accurate high-speed measurement.
Irregularities include corrugation, welds, joints and acoustic roughness. The measurements produced are in a form that can be used directly for prioritisation and planning of maintenance such as grinding and weld straightening.
The HSRCA hardware is relatively simple: accelerometers on both axleboxes of a wheelset and a tachometer. The existing tachometer signal from a service vehicle is normally used. A self-contained system can run on an industry-standard laptop, and the equipment is sufficiently compact that it can be carried by two people. Temporary installation on a vehicle, such as might be undertaken for a short-term survey of a small network, can be completed in less than a day.