-Changed degree-of-freedom (dfw) averages to averaging weighted by degrees-of-freedom uncertainty by changing all the dfw averages from averages weighted by DOF = np_effect to averages weighted by Wi = (1/h_uncrtn)^2. Because this weight is equal to np_effect/dot_sigma, it includes the effect of wave amplitude as well as degrees-of-freedom on uncertainty; the resulting averages weighted by Wi should have the minimum uncertainty. The dfw variable names were not changed but are referred to generically as degree-of-freedom-uncertainty weighted variables. -Made extensive modifications to incorporate h_ice_free to yield DOT in ice-covered waters. ATL07 provides a flag in ATL12 10 m bins indicating the presence of bright leads and h_ice_free is the average of the htybin in these bright lead 10 m bins. In V4 of ATL19, h_ice_free is substituted for h-geoid_seg whenever it appears and h-geoid_seg is taken to represent the top of the ice, h_icetop_geoid, when ice concentration is greater than 15%. A small number of variables are added to outputs, but the previous processing routines are left unchanged when making the substitution of h_ice_free where it exists for h-geoid_seg.