Whereabouts exactly did Yisrael now encamp?
Rashi: They encamped on the north of Mo'av, on a strip of territory that extended from the Emori as far as the River Arnon which belonged to Mo'av. 1
Ramban: They encamped in an area that belonged to the Emori, north of Arnon, a town on the northern border of Mo'av, which was situated on streams that flowed from it.
Seforno: They encamped beside the section of the River Arnon that bordered the Emori but not Mo'av, because the section that bordered Mo'av belonged to Mo'av.
Targum Onkelos: They encamped on the other (north) side of the River Arnon in the desert, on the border of the Emori.
Targum Yonasan: They encamped on the far side of the River Arnon, on the pass in the desert that jutted out from the Emori. 2
Why does the Torah go out of its way to describe their current location?
Rashi: Because Mo'av had refused them entry into their territory, 1 so the Torah informs us that the location where they now encamped did not belong to Mo'av.
Rashi (on Pasuk 15): To relate the miracles that are about to unfold. 2