Complementary filter.

A filter in which the complement of the filter is desired, giving the effect of a high-pass filter by implementing a low-pass filter; a filter for combining multiple data sources, usually of different types, by adding filtered values, where the sum of the filters in the frequency domain is unity; a Kalman filter with fixed gains; Complementary filters are often designed in the frequency domain in way that that the filters determined at build time such that the cutoff frequency of the LFP is equal to that of the HPF. This provides the advantages of DNS's long-term accuracy and INS's short-term accuracy, while filtering DNS's high-frequency noise and INS's slow drift. Compare: averaging filter, Kalman filter;