How do you Time Wake Turb. Separations on Departure

[Foxy Loxy]

I remember being taught in college that vortices are generated from the time the nosewheel lifts, and that's where I time from.

Yep, this is it:

Ref: From MATS 1, Sec1, Ch. 9

9 Vortex Wake Spacing Requirements

9.1.3 Hazardous wake vortices begin to be generated by fixed-wing aircraft when the
nosewheel lifts off the runway on take-off and continues until the nosewheel touches
down on landing.

I time from when the nosewheel detaches from the ground, on that basis.