 This means that formula_2 can be seen as an element of a projective space, that is, two such matrices are considered equivalent if one is a non-zero scalar multiplication of the other.This is a relevant position, for example, if formula_2 is estimated from image data.However, it is also possible to take the position that formula_2 is defined as

where formula_48, and then formula_2 has a well-defined "scaling".