“…Some of the early improvements to the SVSF include a covariance derivation 5,6 , an optimal time varying smoothing boundary width 3,4 , and a strategy for better dealing with missing measurements 4 . In addition, the SVSF has been integrated with Interacting Multiple Model adaptive strategies 5 , a second order SVSF formulation has been derived 7,8 , as has seen many other improvements and applications 9,10,11,12,13,14,15,16 .…”