The logarithm to base ten of the reciprocal of the transmittance.
Symbol: D D = -log10T
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
diameter at the waterline (m)
change in the value of a term
Solar declination angle (in degrees)
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM