For a comprehensive guide to the survey methodology in 2022 and 2023, please see the GBTS Background Quality Report 2022 and the GBTS Background Quality Report 2023, respectively.
Mae WelTAG 2022 yn cyflwyno dull arfarnu cymesur drwy dair lefel o fanylder, WelTAG Byr, WelTAG Safonol a WelTAG Manwl.