Conversation so far:
Why was he considered the father of geography?
Eratosthenes now continued from his knowledge about the Earth.
What was Eratosthenes sketching?
Using his discoveries and knowledge of its size and shape, he began to sketch it.
Were Eratosthenes maps accurate?
Unfortunately, his Geography has been lost to history, but fragments of the work can be pieced together from other great historians like Pliny, Polybius, Strabo, and Marcianus.
Who were Eratosthenes maps used by?
Other great historians like Pliny, Polybius, Strabo, and Marcianus.
How was Eratosthenes able to make such accurate calculations?
He knew that at local noon on the summer solstice in Syene, the Sun was directly overhead.
what are some of the georgaphy terms invented by Eratosthenes that are still used today?
He created terminology that is still used today.

Question: How was he able to achieve this?
Self-contained rewrite: How was Eratosthenes able to achieve this?