FILTER 4DAn adjoint-free four-dimensional variational data

filter 4dA four-dimension (4D) bidirectional dital filter, having a minimum number of delay elements, is presented. This filter, besides having a minimum number of delay elements, also has anOBJECT SET FILTER can be used for input and dialog forms and can be applied to fields and enterable variables that accept an entry filter in the Desn