Air Density (rho) derived from temp, dew point, air pressure and elevation

[5179]

set sub scale 1014.....read height, eg 2000
Guess temp best as......................eg 30C

now.....temp 30C less 15 ...........= 15 x 120 = 1800 ..now add alt height which was 2000 plus this 1800, gives you fairly accurate DA.....of 3800.