Before revision: Emanation graphs of grade k , introduced by Hamedmohseni, Rahmati, and Mondal, are plane spanners made by shooting 2^{k+1}  rays from each given point, where the shorter rays stop the longer ones upon collision.
After revision: Emanation graphs of grade k on a set of points is a plane spanner made by shooting 2^{k+1} rays from each given point, where the shorter rays stop the longer ones upon collision.