Gravitational wave extraction based on Cauchy-characteristic extraction   and characteristic evolution
  We implement a code to find the gravitational news at future null infinity by using data from a Cauchy code as boundary data for a characteristic code. This technique of Cauchy-characteristic Extraction (CCE) allows for the unambiguous extraction of gravitational waves from numerical simulations. 
Maria Babiuc, Bela Szilagyi, Ian Hawke, Yosef Zlochower