All,

My name is Kim, the founder of IP2Location, a geolocation service provider since 2002.

It looks like Tor is looking to review other providers for GeoIP service while I was reading one of a meeting minute for a meeting back in March 2017.

https://trac.torproject.org/projects/tor/wiki/org/meetings/2017Amsterdam/Notes/Metricsin5Years

We are very interested in contributing to Tor and work on this matter. Tor can host and integrate IP2Location LITE (http://lite.ip2location.com) into their application. IP2Location has programming libraries in most languages. We can also work with developers if there is any technical issues.

In term of accuracy, you can find the latest research paper published by TUM. IP2Location has good accuracy as reported in Table V.

Title       : HLOC: Hints-Based Geolocation Leveraging Multiple Measurement Frameworks
Authors     : Quirin Scheitle, Oliver Gasser, Patrick Sattler, Georg Carle from Technical University of Munich (TUM)
PDF Access  : https://arxiv.org/pdf/1706.09331.pdf

Let me know if there is any questions.