4 General construction of time-domain filters for orientation data
1.This paper presents a new scheme that enables us to apply a filter mask 
(or a convolution filter) to orientation data.

2. The majority of signal processing methods cannot be generalized easily to 
orientation data due to the inherent non-linearity of the orientation space.

3.The key idea is to transform the orientation data into their analogues in 
a vector space, to apply a filter mask on them, and then to transform the 
results back to the orientation space.

4. This scheme gives time-domain filters for orientation data that are 
computationally efficient and satisfy such important properties as
coordinate-invariance, time-invariance, and symmetry.