"The Crowd and the Cloud" is a four-part series broadcast during April 2017, which examines citizen science. It shows how smartphones, computers and mobile technology enable regular citizens to become part of a 21st-century way of doing science. The programs also demonstrate how CSs help professional scientists to advance knowledge, which helps speed up new discoveries and innovations. The Crowd & The Cloud is based upon work supported by the National Science Foundation. Since 1975, in order to improve earthquake detection and collect useful information, the European-Mediterranean Seismological Centre monitors the visits of earthquake eyewitnesses to its website and relies on Facebook and Twitter. Citizen science has been used to provide valuable data in hydrology (catchment science), notably flood risk, water quality and water resource management. A growth in internet use and smartphone ownership has allowed users to collect and share real-time flood-risk information using, for example, social media and web-based forms. Although traditional data collection methods are well-established, citizen science is being used to fill the data gaps on a local level, and is therefore meaningful to individual communities. It has been demonstrated that citizen science is particularly advantageous during a flash flood because the public are more likely to witness these rarer hydrological events than scientists. Citizen science includes projects that help monitor plastics and their associated pollution. These include The Ocean Cleanup, #OneLess, The Big Microplastic Survey, EXXpedition and Alliance to End Plastic Waste. Ellipsis seeks to map the distribution of litter using aerial data mapping by unmanned aerial vehicles and machine learning software. A Zooniverse project called The Plastic Tide (now finished) helped train an algorithm used by Ellipsis. Projects that use apps include:  Examples of relevant articles (by date):   Examples of relevant scientific studies or books include (by date):   Citizen sensing can be a form of Citizen science: (quote) "The work of citizen sensing, as a form of citizen science, then further transforms Stengers’s notion of the work of science by moving the experimental facts and collectives where scientific work is undertaken out of the laboratory of experts and into the world of citizens." Similar sensing activities include Crowdsensing and Participatory monitoring. While the idea of using mobile technology to aid this sensing is not new, creating devices and systems that can be used to aid regulation has not been straightforward. Some examples of projects that include citizen sensing are:  Resources for computer science and scientific crowdsourcing projects concerning coronavirus disease 2019 (COVID-19) can be found on the internet or as apps.