If your application is in image processing, you can refer to this as Nipkow scanning, a technique based on the 1884 Nipkow disk, which was the dominant technology in the early days of television.. Electronic “line-by-line” scanning did not come into use until the 1930’s.
Another possibility is radar grid, based on the Plan Position Indicator that we’re all familiar with (at least from movies and TV). This is also a scanning technology, but different in concept from Nipkow scanning, since radar involves sending out a beam of radio waves and measuring the reflections. Nipkow scanning is more like photography, where some of the the light incident on a scene from all directions is reflected towards the camera. The camera is a passive recorder as opposed to an active illuminator.
Of course, your application may lie in a different area where neither television nor radar provide good analogies. The best adjective might simply be the the geometric shape, since terms like grid, mesh, scanning, discretization and the like will carry the meaning of division into small areas.