[citation needed]
Siemens (SIMATIC PCS 7)
https://support.industry.siemens.com/cs/document/109748837/s...
Bosch Sensor Fusion
https://www.bosch-sensortec.com/products/smart-sensors/bha26...
Kalman filters are not state-of-the-art, but they are fairly simple to implement and are still used.