IMHO OpenExr is the way to go when dealing with these files - it's a great format and you can load it as a heightfield or displacement map and, as you mention, preserves the height information in the map.
If your original file is 32bit tiff I'd convert it to OpenExr and use that, as Tangled Universe suggests you can re-export from TG from the heightfield node.
You can do this in Photoshop, but although PS will edit the file in 32bit, it will export it as 16bit half float, (at least it does in CS6, though AFAIK that hasn't changed) There's a free PS Plugin called EXR-IO that will save to full 32bit float:
https://www.exr-io.com/Quote from: Dune on August 23, 2019, 01:49:48 AMit's only a hard B/W image
Only because you're seeing values over 1, just add an Exposure Adjustment layer and drag the exposure down and you can non destructively see your terrain. You can then work in PS with the file, though it has to be said PS is still a bit crap at editing 32bit, and your options are limited.
Quote from: Dune on August 23, 2019, 01:49:48 AMUnless converted to 16-bit, but then it doesn't give me the right altitudes when imported in TG.
I think you chose one of the tone-mapping options when converting to 16bit in PS - that will normalise the values.
I love that Terragen can output "full range" EXRs for heightfields, other progs like World Machine and Gaea normalise their EXRs and you have to figure out the vertical scaling to get it to work in TG