heliarr - two helix convolutions
Initialize: call heliarr_init(nx,aa1,aa2)
Operator : ierr= heliarr_lop(adj,add, xx,yy)
type(filter)
Helix filters
Size of model space where aa1 will be applied
standard operator conventions;
An array of helix convolutions. aa1 Will be applied to points (1:nx1) operator two to the remaining data.
geef90