I did make some lengthy observations about Echolocation on the Ironclaw Mailing List, though -- thoughts that I'd wanted to type up for a while, actually. So, what the heck, let's recycle it -- it has general application to other RPGs, as well.
Echolocation in Ironclaw
While most RPGs that have "Radar Senses" and "Sonar Senses" tend to rule that "all you can see is an outline", they also assume that PCs are humans with "extra" senses grafted onto them. In Ironclaw, we're talking about Bats, anthropomorphic counterparts to real-world chiropterans.
Since I like bats -- and since I worked with sonar systems for much of my college career -- I've spent some time reading up on the subject on the Web. That's where the Echolocation Range = Race Die in Paces rule came from -- it's a good, simple approximation of the ranges of actual bats.
Bear in mind that Echolocation is a sense that evolved to allow a nocturnal flying insectivore to distinguish between a moth and a leaf while performing rapid aerial maneuvers. It's a lot more sensitive and discriminating than just the blip on a radar screen that you see in the movies. If you want a much better visual representation, rent the movie DAREDEVIL*.
Bats can target insects the size of gnats and objects as thin as a human hair. They can determine not only the size, shape and texture of objects around them, but the velocity and direction in which they're moving -- well enough to intercept. They can distinguish between different species of insect, prey species vs. non-prey species. They can chase and catch their targets through tree canopies.
That just might be enough to pick a face out of a crowd in the dark.
Again, I'm assuming strafing tactics rather than sniping tactics.
An Observation Roll wouldn't be inappropriate in such a case, though it might just slow things down.
Personally, I might Observation rolls with Echolocation to pick up some things that sight CAN'T. Someone wearing armor concealed under his tunic? That's gonna give a very different PING.
On the other claw, if you want to read a scroll in the dark, you're still gonna have to light a candle.
*Note that I am recommending DAREDEVIL strictly for the splendid visuals used to represent Murdock's "Radar Sense", not for story, characterization, or quality.
Hmm. Maybe I should rant about Daredevil for a bit... nah, it's been too long since I saw it, and any little damns I might have given have long since faded.
I'll try to have a real post later.