# Mapmaking

This post is a continuation from yesterday.

Tadataka Ino was originally a merchant, but after he turned 50, he started studying astronomy in earnest.

On his observing the North Star, he noticed that the height of the Pole Star was different when he observed it at his house and when he observed it at his teacher's house.

Based on that, he calculated the diameter of the Earth.

His teacher pointed out that the error should be large because the distance is short. So he wanted to go around Hokkaido.

However, at that time, ordinary people were not allowed to travel freely.

Therefore, Mr. Ino promised the government to mapmaking, and he was allowed to go to travel.

He made a lot of astronomical observations on his way mapmaking.

Then he calculated the diameter of the Earth again.

The calculation results are quite accurate compared to the current ones.

Tadataka Ino is famous for mapmaking by walking all over Japan in Edo period.

But It is very interesting for me that his real passion was astronomy.