MM43
The detection range of the TPL looking for a 37.5kHz ULB is 1730 meters when aiming for a 90% reliability of detection.
The TPL is a sort of torpedo-shaped device. Is the 1730m looking along the front centreline, or what? If you think of the search as needing a 'lawn-mower' - i.e. searching in strips - then we'd need to know the strip width and, in hilly terrain, the sensitivity in the vertical axis.