Horizon scanning (HS) or also horizon scan is a method from futures studies, sometimes regarded as a part of foresight.  It is the early detection and assessment of emerging technologies or threats for mainly policy makers in a domain of choice.    Such domains include agriculture,  environmental studies,  health care,  biosecurity,  and food safety. 
Some sources mention HS as an alternative name for environmental scanning (ES),  or view HS as a subset of ES,  or at least suggest ES to have a similar goal to HS.  In summary, ES has key differences to HS.  ES is rather concerned to provide industry specific information for short-term decission making in a competitive environment.   
One of the first usages of the term horizon scanning as related to futures studies appeared in 1995 in a paper discussing trends in information technology and forcasting the year 2005.  Then, horizon scanning was used to name detection and early evaluation of health care technologies in an European workshop in September 1997, whose participants were 27 policy makers and researchers from 12 countries.  This workshop was organized as a part of the European health technology assessment project (HTA).  Policy makers and planners of health services were the main target groups for knowledge produced by horizon scanning.  UK Government's Chief Scientific Advisor's Committee definined horizon scanning in 2004 as: 
"Horizon scanning is the systematic examination of potential threats, opportunities and likely future developments including – but not restricted to – those that are at the margins of current thinking and planning. Horizon scanning may explore novel and unexpected issues, as well as persistent problems or trends."
In 2015, a report by Fraunhofer Institute for Systems and Innovation Research ISI for the European Commission defined HS as: 
"Horizon Scanning is the systematic outlook to detect early signs of potentially important developments. These can be weak (or early) signals, trends, wild cards or other developments, persistent problems, risks and threats, including matters at the margins of current thinking that challenge past assumptions."
A 2013's systematic study of 23 formally established health technology HS programs from different countries identified following common phases in a horizon scanning process: 
- Identify the users of the HS products.
- Estimate the time avalaible for the HS effort.
- Conduct HS, and identify emerging technologies that potentially affect targeted domain.
- Filter the identified technologies by applying criteria for determining the relevance of the technologies to the HS effort.
- Prioritize the technologies that have passed through the filtering process by applying criteria based on stakeholders’ requirements and needs.
- Assess technologies of high priority for the stakeholders, and predict their potential impacts targeted domain.
- Use peer review to check for quality of the HS process and products.
- Disseminate the HS products to the relevant audiences in a timely fashion.
- Update the HS products on a regular basis or when a significant development occurs related to the technology.
|Interviews||Environmental Research Funders Forum Horizon Scanning Study |
|Issue tree||Foresight project on Brain Science, Addiction and Drugs |
|Literature searches and state-of-science reviews|
|Expert workshops||Horizon scan of conservation issues in UK.  Assessment of 100 ecological questions of highest priority to global conservation. |
|Open fora||Future Wiki |
|Delphi questionnaire||50 key issues for the future of Mediterranean wetlands |
|Scenarios||Wildlife Conservation Societies’ Futures of the Wild|
|Systems/Maps||Foresight project on Tackling Obesities: Future Choices |
In order to centralize horizon scanning, UK has founded the English Horizon Scanning Centre (HSC) in 2005.  The Cabinet Office’s Horizon Scanning Secretariat and the Government Office for Science’s Horizon Scanning Centre were combined to the Horizon Scanning Programme team in 2014. 
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