NavList:

We'll say that Lady Southern Cross is due south.

On my screen, Acrux is at 37 mm above the Horizon and Gacrux at 64 mm above the Horizon.

Use their distance 27 mm as a scaling factor for a separation of 6° , almost entirely due to their difference in Declination.

Hence Acrux is at 6° * 37 / (64 -37) = 8.2° above the Horizon.

Since Acrux Declination is at - 63.2° , Acrux is at 26.8° from the South Pole.

The local horizon is at 26.8° - 8.2° = 18.6° from the South Pole.

Hence Observer's Latitude = N 18.6°

Accuracy : I did neglect refraction, actual stars positions, and all the like.

I would guess actual latitude between N18° and N19°

Kermit