[RightDeve]

I remember reading from With Our Backs To Berlin, some remnants of ragtag German soldiers who had no experience in battle, with some Hitlerjugends, shelling a Soviet column with a few mortar tubes. Finished doing that and they went smoking cigarettes and chat around. Just a few minutes later, swooshing sounds came overhead without any gun sound (off-boards large caliber). Before they knew it they were decimated to bits and pieces of human flesh.

And this happened in the Berlin city area, where buildings would severely obstruct LOS. Forward observers and artillerymen (and commanders too) are certainly trained to "triangulate" these out-of-los artillery positions.