u/rocketsocks describes some examples here, but they're mostly minor stuff: https://www.reddit.com/r/AskHistorians/comments/ocif5f/were_there_any_surprises_that_came_when_we_first

Probably most noteworthy is Landsat 1's discovery of an island (later named Landsat island). The island is about 80 feet x 150 feet, a quarter of an acre, too small to hold a football (in any dialect of English!) game on.

Generally though maps were good. It's less about GPS - the first GPS satellite launched in 1978 and obviously by 1978 airliners and ships were crossing the skies all over the world (edit: ships weren't crossing the skies I guess) using radio navigation techniques (the same techniques you'll learn if you were to take up flying today, even if you have GPS in the plane). And people have been able to figure out their latitude and longitude since before radios. And maps will always need some degree of generalization on coastlines (and other similar features - look up the coastline paradox) because those types of naturally occurring features are so geometrically complex that a "true" representation is nearly impossible anyways, so maps then had all the detail they really needed.