From Wartranslated.com, which is a Ukrainian site so factor that in, intercepted phone call between Russian soldiers:
There’s nothing. Everything is for the show. There’s nothing. At all. Their mortars and artillery men fire accurately as f*ck. They’ll shoot, then adjust with drones. A drone is often hanging above us. They have drones with thermal vision for the night, and regular ones for the day. They’ll launch a drone, ours can’t do anything with the drones. They hold them roughly along the *front* line, adjusting. They launch a mortar bomb, it explodes somewhere. They will adjust. Ten bam-bam-bam-bam-bam they put down more, and that’s it. The square is closed. Losses inflicted. Worked well, time to go. That’s how they work. They don’t have some massive authority or something to have 500 bombs in their storages. Not a lot of people. They have like 2-3 people in a crew. They’ll come with a mortar, fire and go.
Pretty smart use of UAV's for ranging..... This is prior to the introduction of HIMARS.