I recently upgraded our PostgreSQL database from 9.2 to 10.1, and I experienced various issues as a result of having installed the old (pre-extension) version of pgsphere. CREATE EXTENSION pg_sphere; failed because the datatypes and functions already existed. The only solution I could find was to DROP all the pgsphere datatypes/functions/etc. with CASCADE first, then pg_upgrade, and then CREATE EXTENSION pg_sphere; would work.

I don't know if that's an issue for anyone else. If it is, maybe this SQL file will save someone some time:

pgsphere_uninstall.txt