How many feet is a single on the grid?

[archolewa]

I've looked through the Angband manual, and haven't been able to find this. I'd like to know because some monsters (like, oh Black Reavers) say that they "Takes quite a while to see intruders, which it may notice from 200 ft." And I'd like to know how many squares away "200 feet" is.

[drquicksilver]

10. look at infra vision. although I don’t know why I think that.

Maybe it was in the manual for Moria ?