∠O=∠ABC=90,OS∨BC,
∴∠ACB=∠ASO,
∴△SOA∽△CBA,
∴ = ,
∴OS=,
∫OA =≈5.5,BC= 1.6,AB= 1.2,
∴OS= ≈7.3,
The depth of the cone pit is about 7.3 meters.
So the answer is: 7.3 meters.