Heat (1995) had 6 months of pre-production, and a 117 day shooting schedule. L.A. Takedown (1989) had 10 days of pre-production, and a 19 day shooting schedule. Michael Mann said that comparing one film to the other is like comparing "freeze dried coffee" to "Jamaican Blue Mountain".
Michael Mann was glad he made L.A. Takedown (1989) because it helped to serve as a prototype for Heat (1995) and gave him the chance to see what worked and what didn't work, to play around with it, and to get deeper into it. He never planned on the TV film being a prototype, but it ended up being that way and it helped Mann to get "Heat" the way he wanted it.
This was originally meant to be a pilot for a new television series, but it never materialized, so Michael Mann remade the movie into Heat (1995). However, eventually, Mann did create a series inspired by this, called Robbery Homicide Division (2002).
The original 180 page screenplay predates both L.A. Takedown (1989) and Heat (1995), it was written in the late 70s and then revised after Michael Mann had finished Le Solitaire (1981). When making the TV movie version, Mann had to severely abridge the original script and abstracted around 110 pages from the 180 page script, making the TV movie not fully developed compared to the later cinematic version.
Shot in only two weeks.