I sat in shock for the remainder of the presentation thinking of the complexity and all the math involved. After their presentation, I mentioned this to the presenter offline, who replied “it’s very hard and complex work, yes”.
Fast forward around 2002 and it turns out they were indeed using proj.4 which initially made me think, “ah, that’s easy, then”.
These days, I would say well it’s not that easy. Integration, upstream changes, versions, packaging and deployment. Moving parts. Different issues. It’s smart, strategic and preferable not to re-invent the wheel and use existing libs, but the work certainly doesn’t end there.
(For what it’s worth, the vendor [it doesn’t matter who they are] and their product are still around and going strong)