In 1st Group back in the 1990s, there was a guy in the Sniper Committee who was big on the use of a Theodolite for ELR with the .50 BMGs. Theodolites use registered optics against angular measurements to determine range exactly, down to seconds of arc, with resection.
They are/were common in surveying before total stations were adopted. There are a lot of laser-based systems in surveying now.
With a mechanical-optical Theodolite, you could have one as part of your spotting scope with an arc second window or other methods using basic existing optical systems present in a Sniper Team/Section.
It’s something I’ve been working on for years as part of a passive solutions set to avoid compromising EMCON. I’ve never been comfortable with the amount of IR spectrum emissions common to dismounts from LRFs and LAMs.