Just putting this out there. This is one area where Esri's software really shines. They have so many software offerings and so much is said about different things you can do with ArcGIS (and competing systems), but the capability of their projection engine and geocoding systems - the code that lies at its heart - is unmatched, by far, at least as of 5 years ago when I left for a different company.
I had long conversations with Esri's projection engine lead. Really remarkable guy - he's got graduate degrees in geography and math (including a PhD) and he's an excellent C/C++ developer. That kind of expertise trifecta is rare. I'd walk by his office and sometimes see him working out an integral of a massive equation on his whiteboard (not that he didn't also use a CAS). "Oh yeah, I'm adding support for a new projection this week."
Many people don’t appreciate the extent that building robust geospatial systems requires seriously hardcore mathematics and physics skills. All of the mapping companies have really smart PhDs wrangling with these problems. I’ve always enjoyed talking with them about the subtleties of the challenges. There are so many nuances that never occurred to me until they mentioned them.
I had long conversations with Esri's projection engine lead. Really remarkable guy - he's got graduate degrees in geography and math (including a PhD) and he's an excellent C/C++ developer. That kind of expertise trifecta is rare. I'd walk by his office and sometimes see him working out an integral of a massive equation on his whiteboard (not that he didn't also use a CAS). "Oh yeah, I'm adding support for a new projection this week."