 the ZUPT window time
            lat_e(i) = mean (lat_e(i-idz:i , :));
            lon_e(i) = mean (lon_e(i-idz:i , :));
            h_e(i)   = mean (h_e(i-idz:i , :));

            % Alternative attitude ZUPT correction
            % roll_e(i)  = (roll_e(i-idz , :));
            % pitch_e(i) = (pitch_e(i-idz , :));
            % yaw_e(i)   = (yaw_e(i-idz, :));
            % lat_e(i) = (lat_e(i-idz:i , :));
            % lon_e(i) = (lon_e(i-idz:i , :));
            % h_e(i)   = (h_e(i-idz:i , :));

       