  We present details of improvements to data processing and analysis which were
recently used for a re-reduction of the Very Large Array (VLA) Low-frequency
Sky Survey (VLSS) data. Algorithms described are implemented in the
data-reduction package Obit, and include smart-windowing to reduce clean bias,
improved automatic radio frequency interference removal, improved bright-source
peeling, and higher-order Zernike fits to model the ionospheric phase
contributions. An additional, but less technical improvement was using the
original VLSS catalog as a same-frequency/same-resolution reference for
calculating ionospheric corrections, allowing more accuracy and a higher
percentage of data for which solutions are found. We also discuss new
algorithms for extracting a source catalog and analyzing ionospheric
fluctuations present in the data. The improved reduction techniques led to
substantial improvements including images of six previously unpublished fields
(1% of the survey area) and reducing the clean bias by 50%. The largest angular
size imaged has been roughly doubled, and the number of cataloged sources is
increased by 35% to 95,000.
