The 3Pi+ has an electronic compass (LIS3MDL) which if properly calibrated, can be used to determine the direction of travel, or as an aid in making more accurate 90 degree turns. To learn more about magnetometer calibration, see this post: Correcting the Balboa magnetometer
Likewise, the rate gyro in the onboard IMU (LSM6DS33) can be used to independently measure rotations about the vertical axis.