I would guess power line inspection also because I have major powerlines running nearby and once witnessed what looked like an early Cessna 170 / O-1 Bird Dog flying erratically 200 to 300 feet up, following the powerlines and it was so wobbly and all over the place I thought the pilot was drunk. It was like something out of a movie. They did laps, back and forth and checking the flight radar revealed their tracks and it all made sense. Was very exciting to run out when it was coming back and spotting it again!