What is cat II and cat III?

Cat II and Cat III most commonly refer to Category II and Category III instrument landing system approaches in aviation, which allow landing in progressively lower visibility, or Category II and III CPT codes in medical billing for quality tracking and emerging technology. In aviation, CAT II approach allows landing with decision height 100 feet and runway visual range 1200 feet in fog, requiring more precise ground equipment, aircraft with autoland, and crew certification, while CAT III is even more precise, subdivided into IIIA decision height below 100 feet RVR 700 feet, IIIB below 50 feet RVR 150 feet, and IIIC zero-zero true blind landing with no visual reference, requiring full autoland and rollout guidance and special runway lighting. CAT III allows airports to stay open in dense fog. In medical billing, Category II codes are optional tracking codes starting with F for quality measurement like 2023F dilated eye exam, not paid, while Category III codes are temporary T-codes for emerging technology like new robotic surgeries, used for data collection for up to 5 years then may become Category I or be deleted. In tractors, Cat II and Cat III refer to hitch sizes, Cat II for 40 to 100 horsepower with 1-1/8 inch pins and lift up to 5000 pounds, Cat III for 80 to 225 horsepower with 1-7/16 inch pins and lift up to 8000 pounds, Cat III bigger and stronger.