A proposal for Charleston: Line callers who are not visually impaired

In today's match between Venus Williams and Sania Mirza, the line calling was beyond questionable. In the third set, there was muttering (and more) in the stands when linespeople made obviously bad calls at least four--and maybe five--times in a row, none of which was corrected by the chair umpire. In every case, the call was incorrectly made against Sania Mirza (or in favor of Venus Williams, depending on your point of view). Once is expected, twice is unprofessional. But this series of calls effectively took away Mirza's chance of taking the third set to a more competitive edge.