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We improve our filament automated detection method which was proposed in ourprevious works. It is then applied to process the full disk H$\alpha$ datamainly obtained by Big Bear Solar Observatory (BBSO) from 1988 to 2013,spanning nearly 3 solar cycles. The butterfly diagrams of the filaments,showing the information of the filament area, spine length, tilt angle, and thebarb number, are obtained. The variations of these features with the calendaryear and the latitude band are analyzed. The drift velocities of the filamentsin different latitude bands are calculated and studied. We also investigate thenorth-south (N-S) asymmetries of the filament numbers in total and in eachsubclass classified according to the filament area, spine length, and tiltangle. The latitudinal distribution of the filament number is found to bebimodal. About 80% of all the filaments have tilt angles within [0{\deg},60{\deg}]. For the filaments within latitudes lower (higher) than 50{\deg} thenortheast (northwest) direction is dominant in the northern hemisphere and thesoutheast (southwest) direction is dominant in the southern hemisphere. Thelatitudinal migrations of the filaments experience three stages with decliningdrift velocities in each of solar cycles 22 and 23, and it seems that the driftvelocity is faster in shorter solar cycles. Most filaments in latitudes lower(higher) than 50{\deg} migrate toward the equator (polar region). The N-Sasymmetry indices indicate that the southern hemisphere is the dominanthemisphere in solar cycle 22 and the northern hemisphere is the dominant one insolar cycle 23.

Statistical Analysis of Filament Features Based on the H{\alpha} Solar Images from 1988 to 2013 by Computer Automated Detection Method