Underpass is a customizable data engine that processes mapping data.
It updates a local copy of the OSM database in near real-time, and provides customizable statistics and validation reports. It is designed to be high performance on modest hardware.
We've deployed a basic demo that keeps a database up-to-date for (some country), rendering buildings and highlighting the ones identified as "un-squared":
https://underpass.live (currently unavailable, working on it)
Check the documentation
Check the tasks board and roadmap here
This is an exciting project, its core is made with C++ but it also includes a Python API and there are UI components for interacting and visualizing data.
You can learn a lot contributing to Underpass, while helping the FOSS and mapping communities, get involved!
Underpass is free software! you may use any Underpass project under the terms of the GNU General Public License (GPL) Version 3.