I am demo'ing the MarketDelta with IQFeed and I notice that you are able to load historical tick data to backfill the footprint chart. I'm curious if anyone knows how MarketDelta is able to reconstruct a footprint chart with only "post trade" tick data. It was my understanding that you need pre-trade (best bid/offer) to accurately calculate what is an print on the bid or offer, which is what MarketDelta is based upon. Or is it possible that IQFeed also provides the best bid/offer along with the historical tick information? (E.g., time,bid,offer,price,volume).