7.2 Sources of data

EPA’s CMV estimates are computed using detailed Automatic Identification System (AIS) activity data collected by terrestrial receivers maintained by the US Coast Guard in conjunction with commercially sourced AIS data collected by satellites. The details of these calculation are available in the documents 2023NEI_C1C2_Documentation and 2023 C3 Marine Emissions Tool Documentation on the 2023 Supporting data FTP site. Two states submitted CMV emissions to EIS (California and Texas). After review, EPA determined to use EPA estimates for the 2023 NEI instead of California’s estimates. Texas’s CMV emissions were deemed acceptable. These decisions were based on both methodology and resulting estimates.