As said before, for noisy data, the system equation, *Q(x,y)=0* in
the case of conic fitting, can hardly hold true. A common practice
is to directly minimize the *algebraic distance* ,
i.e., to minimize the following function:

Clearly, there exists a trivial solution *A=B=C=D=E=F=0*.
In order to avoid it, we should normalize *Q(x,y)*. There are many
different normalizations proposed in the literature. Here we describe
three of them.

Thu Feb 8 11:42:20 MET 1996