Can't find a source at the moment but cool side anecdote to this...working from memory

Honeywell was largely the driving force behind developing terrain avoidance systems for commercial aircraft. Those initial systems worked based on comparing the terrain below to the flight profile of an aircraft using a radar altimeter.

There was a CFIT (controlled flight into terrain) accident (I want to say AA in Peru?) where the mountains basically got to tall to fast to give the crew sufficient time to react because of that system. That caused Honeyweell to go back and look at ways to improve the system to be predictive rather than reactive - using a terrain database.

Honeywell bought/came into posession of a russian world wide terrain altitude database to do the first generation of this. I can only imagine the US had the same thing, or more accurate, but this was far enough ago that US Government wasn't sharing.