The GLONASS system is good enough to get one to the general area of a target, but I sure wouldn’t want to use it for anything critical. It has a minimum inherent vertical error of +/- 70 *meters* and a minimum horizonal error of 57 *meters*.
Compare that to GPS, which starts off with a base error of only 30 *centimeters* (about a foot or so).
That said, the GLONASS satellites are surprisingly large (1400+kg) when compared to a GPS satellite (770kg) and appear to have an antenna complex on them that doesn’t have anything to do with the primary purpose of broadcasting navigation signals.
You’ve got me more interested now. I’m going to have to do some research. I’ve owned a couple of handheld GPS units for close to ten years, so I’m a bit familiar with GPS but not the GLONASS.