Conversation so far:
What is the brief definition of Lewis Fry Richardson's research?
Lewis Fry Richardson decided to search for a relation between the probability of two countries going to war and the length of their common border.
Why did Lewis Fry Richardson start research on the relation between the probability of two countries going to war and the length of their common border?
For example, the border between Spain and Portugal was variously quoted as 987 or 1214 km, and that between the Netherlands and Belgium as 380 or 449 km.

Question: How did he find the length of the two borders?
Self-contained rewrite: How did Lewis Fry Richardson find the length of the two borders?