Provided are an avalanche photodiode and a method of fabricating the same. In one example, satellite signals are processed at each of a plurality of reference stations to receive a respective plurality of satellite navigation data streams. If the scanning operation is taking place within a terminal server type of environment, such as the Microsoft Terminal Server, where an application program is run in a virtual execution environment, then provision is made to identify client connections to the server so that error messages can be presented to a terminal server clients terminal, rather than at the terminal server console. An internal rack, in particular, including several levels, can be located inside the external casing.