were large ruggedized 'M210 RTK' quadcopters with thermal and 3d imaging technology, eleven were smaller 'Mavic Pro' quadcopters measuring less than two feet in diameter, and one was a 'DJI Inspire' quadcopter intended for training purposes. The drones are manned by two officers from the NYPD's Technical Assistance Response Unit, one who monitors the drone and the other who controls it. Policies on the use of drone technology include that it will not use facial recognition and will only be deployed to monitor pedestrian and vehicle congestion and for security observation at shootings and large scale events. Additionally, the chief of police can approve drone use for public safety or emergency situations. Critics such as the NYCLU argue that the generality of the term 'large scale events' allows for drones to be used in a broad range of applications, including the monitoring of protestors and activists. They also argue that although the drones themselves cannot perform facial recognition as per the policy, the footage collected from drones can still be used for such purposes. As with other video collected by the NYPD, drone footage is retained for a minimum of 30 days upwards to an indefinite period if needed for unspecified legal purposes. Police officials state that the drones will not be used for unlawful surveillance, and will not be equipped with weapons. Further they state that it is negligent to not use drone technology. Governance and policy NYPD self-governance In April 2009, the NYPD released privacy guidelines for the domain awareness system's usage of data, specifying regulations such as data collection being utilized only in public areas and the DAS not using facial recognition. In 2012 Olivia J. Greer provided criticism of the NYPD privacy guidelines in the Michigan Telecommunications and Technology Law Review, stating that "the NYPD and the Guidelines make it clear that “flexibility” is required to protect the public, and are very unclear with regard to how much and what type of flexibility is required. [...] Of overarching concern is the fact that the Guidelines allow data to be used for indeterminate “legitimate law enforcement and public safety purposes” beyond the scope of the Statement of Purpose. This effectively means that data may be used for any purpose identified by the NYPD to relate to law enforcement, but not encompassed in the Guidelines. Perhaps the most troubling aspect of the Guidelines appears in the final paragraph: