Hi TandemMotor.
With ref LVP's (in the UK).
Check out MATS (part 1) Section 7, Chapter 1, Paragraph 3.1 (phew...)
That gives brief details, (and Im quite new to this game, so my apologies if Im incorrect).
As I understand it, the broadcast made from the tower or on the atis contains the figures that ATC would quote each time it is required, (eg - pre take off roll, approach, landing etc)... However, if a pilot observes the situation to be WORSE than what is being broadcast the official RVR quote will be FOLLOWED with "Unofficial observation from a departing A/C at time (xx) was RVR x,y,z."
As I understand, we're not allowed to just change the broadcast, but we are allowed to add the "unofficial observation" thing to it.
Hope this helps.
Bri.
