Universal standard for a CAT-I approach at DH [typically 200 feet AGL] if you can see the approach lights, but not the threshold just yet, you may continue the descent over the lights to 100 feet, at which point you must see the runway or execute a go-round.
CAT-II DH 100'
CAT-IIIa Alert Height 50'
CAT-IIIb Alert Height 20'
Radar altitude height as measured from extended landing gear to ground.