There has been a lot of changes to the building code for decks over the years. Most older decks do not meet code and need to be inspected and updated as required to maintain a safe deck.
Challenging Footings. Large Basalt Boulders prevented the footings from being buried below frost. Footings were attached with rebar to the Basalt.
Using a Lazer Level and a little Math, determining the column lengths become very easy
Removing a Wall can sure open up a space.