In article 1108887431.292438@idlweb, . wrote:
Hi All
Does anyone know the mathematical equation to work out the "drift
correction" and "ground speed" without using the computer.


It's "trivial". the mathematical subject is "vector algebra.
As applied to flying, the magic phrase is "wind triangle".
You can solve "graphically", or numerically. The latter requires a
set of "trig tables".

The actual equation is:
"indicated airspeed/direction" + "wind speed/direction" =
"speed-over-ground/direction"