Filtered_kernel<CK>is a kernel that uses the filtering technique based on interval arithmetic from [BBP01] to achieve exact and efficient predicates. In addition, a few selected important predicates are implemented using the formally proved, semistatic, filtering techniques from [MP05].
The geometric constructions are exactly those of the kernel CK, which means that they are not necessarily exact.
#include <CGAL/Filtered_kernel.h>

 The type of the exact kernel. 

 The type of the approximate "filtering" kernel. 
The following example shows how to produce a kernel whose geometric objects and constructions are those of Simple_cartesian<double> but the predicates are exact.
#include <CGAL/Simple_cartesian.h> #include <CGAL/Filtered_kernel.h> typedef CGAL::Simple_cartesian<double> CK; typedef CGAL::Filtered_kernel<CK> K;