1. Compared with the time-wise and the space-wise approaches to recover the gravity field from GOCE data, the invariant approach is stated briefly.

2. The different filter methods for the time-wise, the space-wise and the invariant approaches are described here. In fact, the key problem to deal with GOCE data is how to filter SGG data (Satellite Gravity Gradients).

3. The relations between MBW (Measured Bandwidth) and the degree/order of the gravity field are shown here. In fact, it is the constraint for bandwidth measurement of SGG to make the solved GOCE gravity field be incomplete. A new idea is proposed to overcome such incompleteness.

4. It is discussed how to assess the accuracy of SGG.