The weapon officer determines (after consultations with God
)the AOB as it looks from where you are, the bearing and speed and range. After that the TDC calculates (automatically) how much the torpedo needs to turn to hit it, based on how you turn the periscope/UZO. Except, the TDC cannot update the range as the target closes with you, so you (or the weapon officer) needs to reset it before firing after a long wait. The weapon officer doesn't have to worry about the gyro angle itself. It's the end result.