The Operator of the Airport is responsible, under ICAO standards,to measure the depth of snow or slush or water by means of a simple standard depth gauge. Readings are taken at approximately 300 metre intervals between 5 & 10 metres either side of centre line & clear of the effects of rutting. Depth information is given in millimetres for each third of the total runway, each being the mean of the reading obtained.
Additionally, when making these measurements observers carrying out the runway inspection will make an assessment of the nature of the surface covering, which will be described in the following categories:
(a) Dry snow (up to but not including 0.35 S.G)
(b) Wet snow (0.35 S.G.up to but not including 0.5 S.G.)
(c) Compacted snow (over 0.5 S.G.)
(d) Slush (0.5 S.G. to 0.8 S.G.)
(e) Standing water (1.0 S.G.)
Wait, this sounds to omit a lot of possibilities.
The depth of solid ice (S. G. 0,91) may be difficult to measure and irrelevant to braking action, of course. But why is slush specified as 0,5 S. G. to 0,8 S. G? It should surely be 0,91 to 1,00 S. G?