The GoPiGo3 encoders can measure forward distance traveled to 0.5 mm and regularly achieve 2 mm accuracy on dusty polished wood floors, but when it comes to measuring heading changes the GoPiGo3 encoders simply cannot do better than +/- 45 degrees over time, and +/- 5 degrees during a “straight drive”.
ROS localization in a known map has the potential to use the LIDAR scan with the GoPiGo3 encoders to improve the pose estimation (location plus heading).
I have posted some localization questions on the robotics stackexchange forum that may be of interest to anyone exploring localization on the GoPiGo3.