The Intelligence Authorization Act of 2021 contained a section titled "Sec. 612. Research partnership on activities of People's Republic of China" that directed the National Geospatial-Intelligence Agency (NGA) to:
(1) REQUIREMENT.—Not later than 180 days after the date of the enactment of this Act, the Director of the National Geospatial-Intelligence Agency shall seek to enter into a partnership with an academic or non-profit research institution to—
(A) carry out joint unclassified geospatial intelligence analyses of the activities of the People’s Republic of China that pose risks to the national security interests of the United States; and
(B) make available on a publicly available internet website unclassified geospatial intelligence products relating to such analyses.
Tearline is the "publicly available internet website" used to carry out the Congressional Directed Action (CDA) for hosting China content. Tearline launched in April 2018, several years before being utilized for the CDA in 2021.
The CDA also directs certain topics to be covered publicly such as military modernization, global infrastructure projects, and environmental and climate change issues resulting from Chinese practices.
For further details see Sec. 612 of the Consolidated Appropriations Act, 2021.