What are the B, C, H and T prefixes in the Passive Station Number?
A. The letter prefix in the Passive Station numbering system is largely a historical one indicating the origins of the station. Stations prefixed with the letter ‘B’ are stations originally included in the SciNet (EUREF GB92) network of stations. Before the Active GPS Network these were of a higher order, however there is no longer any difference in quality between any of the designated Passive Layer stations. Stations prefixed with the letter ‘C’ are stations which originally met the criteria for a National Network GPS (Passive Layer) station. Namely: have good aspect of the sky for GPS occupation; be accessible 24 hours a day to a two-wheel drive vehicle in all weather conditions; and permission for access, if required, easy to obtain. Most of these monuments were constructed specifically for GPS use, though where suitable, existing Fundamental Bench Mark or Triangulation monuments were adopted. Stations prefixed with the letter ‘H’ or ‘T’ are Fundamental Bench mark or Triangulation
