system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did people know what the world looked like before satellites?

How did people back i the day know the shape of countries and oceans look like without a clear view from space? How did they make accurate globes and maps back then?
gpt
They made land measurements, i.e. they determined distances and angles between various landmarks through a process called triangulation. This involves looking from two different points with a known distance between them (baseline) at some distant third point (or landmark). The difference in view angles allows one to calculate the distance to the third point. Now the calculated distance can be used as a baseline for a new triangulation, and so on. People also could make measurements of coordinates for different locations through careful observation and measurement of positions of the Sun and stars. Covering an entire country in triangles paired and adjusted to coordinate measurements will provide one with a map of a country.