Autoland expalnation
An ILS can be CAT I, II, IIIa, IIIb or IIIc. CAT I has aircraft critical areas surrounding the GP antenna and the LOC antenna. The GP critical area is fairly small whereas the LOC critical area is within the runway strip and within 1 mile of the LOC antenna. These are often more accurately mapped in documents to assist ATC. Within the aircraft critical areas there are smaller vehicle critical areas. Aircraft and vehicles in these areas can disturb the ILS signals to aircraft on final which may cause deviations from the ILS path.
For CAT II or III operations there is an added sensitive area surrounding the runway. It is 90 metres wide at the LOC antenna and splays out for about 1 1/2 miles to 180 metres wide, then parallels the runway to north of the threshold.
During CAT I or visual conditions aircraft notify ATC if they are making an autoland so ATC can advise the crew whether the areas are protected, which they are generally not due to normal surface operations. Crews make practice autolands both for crew and aircraft currency. An assessment of the landing can then be made taking protection into consideration.
During CAT II or III operations, all landings are autoland and the critical and sensitive areas are protected when an aircraft is within a 4 and 2 mile final respectively. This is done by spacing landings and departures to allow preceding aircraft to vacate the areas and by managing other surface traffic.
Low visibility operations are one of the times in ATC where there is less traffic but the tower works harder to manage it.