Search This Blog

Saturday, August 24, 2024

OpenStreetMap

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/OpenStreetMap
 
OpenStreetMap
OpenStreetMap homepage, showing the world map
Available in96 languages and variants, local languages for map data
Country of originUnited Kingdom
OwnerOpenStreetMap Foundation
Created bySteve Coast
ProductsEditable geographic data, tiled web map layer
URLwww.openstreetmap.org
CommercialNo
RegistrationRequired for contributors, not required for viewing
Users10.6 million[2]
Launched9 August 2004; 20 years ago [3]
Current statusActive
Content license
Open Database License

OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveys, trace from aerial imagery and also import from other freely licensed geodata sources. OpenStreetMap is freely licensed under the Open Database License and as a result commonly used to make electronic maps, inform turn-by-turn navigation, assist in humanitarian aid and data visualisation. OpenStreetMap uses its own topology to store geographical features which can then be exported into other GIS file formats. The OpenStreetMap website itself is an online map, geodata search engine and editor.

OpenStreetMap was created by Steve Coast in response to the Ordnance Survey, the United Kingdom's national mapping agency, failing to release its data to the public under free licences in 2004. Initially, maps were created only via GPS traces, but it was quickly populated by importing public domain geographical data such as the U.S. TIGER and by tracing permitted aerial photography or satellite imagery. OpenStreetMap's adoption was accelerated by Google Maps's introduction of pricing in 2012 and the development of supporting software and applications.

The database is hosted by the OpenStreetMap Foundation, a non-profit organisation registered in England and Wales and is funded mostly via donations.

History

The founder of OpenStreetMap, Steve Coast, in 2009

Steve Coast founded the project in 2004 while at a university in Britain, initially focusing on mapping the United Kingdom. In the UK and elsewhere, government-run and tax-funded projects like the Ordnance Survey created massive datasets but declined to freely and widely distribute them. The first contribution was made in London in 2005. In April 2006, the OpenStreetMap Foundation was established to encourage the growth, development and distribution of free geospatial data and provide geospatial data for anybody to use and share.

In April 2007, Automotive Navigation Data (AND) donated a complete road data set for the Netherlands and trunk road data for India and China to the project. By July 2007, when the first "The State of the Map" (SotM) conference was held, there were 9,000 registered users. In October 2007, OpenStreetMap completed the import of a US Census TIGER road dataset. In December 2007, Oxford University became the first major organisation to use OpenStreetMap data on their main website. Ways to import and export data have continued to grow – by 2008, the project developed tools to export OpenStreetMap data to power portable GPS units, replacing their existing proprietary and out-of-date maps. In March 2008, two founders of CloudMade, a commercial company that uses OpenStreetMap data, announced that they had received venture capital funding of €2.4 million.

Yahoo! (2006–2011), Bing (2010 – till date), and DigitalGlobe (2017–2023) allowed their aerial photography, satellite imagery to be used as a backdrop for map production. For a period from 2009 to 2011, NearMap Pty Ltd made their high-resolution PhotoMaps (of major Australian cities, plus some rural Australian areas) available under a CC BY-SA licence.

In 2012, the launch of pricing for Google Maps led several prominent websites to switch from their service to OpenStreetMap and other competitors. Chief among these were Foursquare and Craigslist, which adopted OpenStreetMap, and Apple, which ended a contract with Google and launched a self-built mapping platform using TomTom and OpenStreetMap data.

Data

Data structure

see caption
Illustration of OpenStreetMap data primitives (nodes, ways and relations)

OpenStreetMap uses a topological data structure, with four core elements (also known as data primitives):

  • Nodes are points with a geographic position, stored as coordinates (pairs of a latitude and a longitude) according to WGS 84. Outside of their usage in ways, they are used to represent map features without a size, such as points of interest or mountain peaks.
  • Ways are ordered lists of nodes, representing a polyline, or possibly a polygon if they form a closed loop. They are used both for representing linear features such as streets and rivers, and areas, like forests, parks, parking areas and lakes.

  • Relations are ordered lists of nodes, ways and relations (together called "members"), where each member can optionally have a "role" (a string). Relations are used for representing the relationship of existing nodes and ways. Examples include turn restrictions on roads, routes that span several existing ways (for instance, a long-distance motorway), and areas with holes.
  • Tags are key-value pairs (both arbitrary strings). They are used to store metadata about the map objects (such as their type, their name and their physical properties). Tags are not freestanding, but are always attached to an object: to a node, a way or a relation. A recommended ontology of map features (the meaning of tags) is maintained on a wiki. New tagging schemes can always be proposed by a popular vote of a written proposal in OpenStreetMap wiki, however, there is no requirement to follow this process. There are over 89 million different kinds of tags in use as of June 2017.

The OpenStreetMap data primitives are stored and processed in different formats. OpenStreetMap server uses PostgreSQL database, with one table for each data primitive, with individual objects stored as rows. From this, several database dumps are created, which are available for download. The complete dump is called planet.osm. These dumps exist in two formats, one using XML and one using the Protocol Buffer Binary Format (PBF).

License

OpenStreetMap data and derived tiles were originally published under the Creative Commons Attribution-ShareAlike licence (CC BY-SA) with the intention of promoting free use and redistribution of the data.

In September 2012, the licence was changed to the Open Database Licence (ODbL) published by Open Data Commons (ODC) in order to define its bearing on data rather than representation more specifically. As part of this relicensing process, some of the map data was removed from the public distribution. This included all data contributed by members that did not agree to the new licensing terms, as well as all subsequent edits to those affected objects. It also included any data contributed based on input data that was not compatible with the new terms.

Estimates suggested that over 97% of data would be retained globally, but certain regions would be affected more than others, such as in Australia where 24 to 84% of objects would be retained, depending on the type of object. Ultimately, more than 99% of the data was retained, with Australia and Poland being the countries most severely affected by the change.

All data added to the project needs to have a licence compatible with the Open Database Licence. This can include out-of-copyright information, public domain or other licences. Software used in the production and presentation of OpenStreetMap data may have separate licensing terms.

Map tiles provided by the OpenStreetMap project were licensed under CC-BY-SA-2.0 until 1 August 2020. The ODbL license requires attribution to be attached to maps produced from OpenStreetMap data, but does not require that any particular license be applied to those maps. "©OpenStreetMap Contributors" with link to ODbL copyright page as attribution requirement is used on the site.

Map making

Data sources

Editing with JOSM after a ground survey

Map data is collected by ground survey, personal knowledge, digitizing from imagery, and government data. Ground survey data is collected by volunteers traditionally using tools such as a handheld GPS unit, a notebook, digital camera and voice recorder.

Software applications on smartphones (mobile devices) have made it easy for anybody to survey. The data is then entered into the OpenStreetMap database using a number of software tools including JOSM and Merkaator.

Mapathon competition events are also held by local OpenStreetMap teams and by non-profit organisations and local governments to map a particular area.

The availability of aerial photography and other data from commercial and government sources has added important sources of data for manual editing and automated imports. Special processes are in place to handle automated imports and avoid legal and technical problems.

Surveys and personal knowledge

Surveying routes with a satellite navigation device

Ground surveys are performed by a mapper, on foot, bicycle, or in a car, motorcycle, or boat. Map data was typically recorded on a GPS unit or on a smart phone with mapping app.

Once the data has been collected, it is entered into the database by uploading it onto the project's website together with appropriate attribute data. As collecting and uploading data may be separated from editing objects, contribution to the project is possible without using a GPS unit, e.g. by using Paper mapping.

Similar to users contributing data using GPS unit, corporations (e.g. Amazon) with large vehicle fleets use telemetry data from the vehicles to contribute data to OpenStreetMap.

Some committed contributors adopt the task of mapping whole towns and cities, or organising mapping parties to gather the support of others to complete a map area.

A large number of less active users contribute corrections and small additions to the map.

Satellite/Aerial images

Maxar, Bing, ESRI, and Mapbox are some of the providers of aerial/satellite imagery which are used as a backdrop for map production.

Street-level image data

Data from several street-level image platforms are available as map data photo overlays. Bing Streetside 360° image tracks, and the open and crowdsourced Mapillary and KartaView platforms provide generally smartphone and windshield-mounted camera images. Additionally, a Mapillary traffic sign data layer, a product of user-submitted images is also available.

Government data

Some government agencies have released official data on appropriate licences. This includes the United States, where works of the federal government are placed under public domain. In the United States, most roads originate from TIGER from the Census Bureau. Geographic names were initially sourced from Geographic Names Information System, and some areas contain water features from the National Hydrography Dataset. In the UK, some Ordnance Survey OpenData is imported. In Canada Natural Resources Canada's CanVec vector data and GeoBase provide landcover and streets.

Globally, OpenStreetMap initially used the prototype global shoreline from NOAA. Due to it being oversimplified and crude, it has been mainly replaced by other government sources or manual tracing.

Out-of-copyright maps can be good sources of information about features that do not change frequently. Copyright periods vary, but in the UK Crown copyright expires after 50 years and hence old Ordnance Survey maps can legally be used. A complete set of UK 1 inch/mile maps from the late 1940s and early 1950s has been collected, scanned, and is available online as a resource for contributors.

Contributors

Field survey in various parts of the Guagua by a group of mappers. They took notes and photos, and recorded GPS tracks. Shown in the photo is the Betis group standing beside one of the Death March trail monuments.

The project has a geographically diverse user-base, due to emphasis of local knowledge and "on-the-ground" situation in the process of data collection. Many early contributors were cyclists who survey with and for bicyclists, charting cycleroutes and navigable trails. Others are GIS professionals who contribute data with an extension for ArcGIS. Contributors are predominately men, with only 3–5% being women.

By August 2008, shortly after the second The State of the Map conference was held, there were over 50,000 registered contributors; by March 2009, there were 100,000 and by the end of 2009 the figure was nearly 200,000. In April 2012, OpenStreetMap cleared 600,000 registered contributors. On 6 January 2013, OpenStreetMap reached one million registered users. Around 30% of users have contributed at least one point to the OpenStreetMap database.

As per a study conducted in 2011, only 38% of members carried out at least one edit and only 5% of members created more than 1000 nodes. Most members are in Europe (72%). According to another study, when a competing maps platform is launched, OSM attracts fewer new contributors and pre-existing contributors increase their level of contribution possibly driven by their ideological attachment to the platform. Overall, there is a negative effect on the quantum of contributions.

Commercial contributors

Some companies freely license satellite/aerial/street imagery sources from which OpenStreetMap contributors trace roads and features, while other companies make data available for importing map data. Automotive Navigation Data (AND) provided a complete road data set for Netherlands and trunk roads data for China and India. In June 2018, the Microsoft Bing team announced contribution of 125 million U.S. building footprints to the project – four times the number contributed by users and government data imports. Amazon uses OpenStreetMap for navigation and has a team which revises the map based on GPS traces and feedback from its drivers. As of February 2021, Apple was the most prolific corporate editor, responsible for 80% of edits to existing roads.

According to a study, nearly 17% of all edits to the map came from corporate teams during 2019–2020. The top 13 corporate contributors during 2014–2020 include Apple, Kaart, Amazon, Facebook, Mapbox, Digital Egypt, Grab, Microsoft, Telenav, Developmentseed, Uber, Lightcyphers and Lyft. There was some vandalism on some occasions attributed to corporate editors.

Non-governmental organisations

Humanitarian OpenStreetMap Team (HOT) is a nonprofit organisation promoting community mapping across the world. It developed the open source HOT Tasking Manager for collaboration, and contributed to mapping efforts after the April 2015 Nepal earthquake, the 2016 Kumamoto earthquakes, and the 2016 Ecuador earthquake. The Missing Maps Project, founded by the American Red Cross, Doctors Without Borders, and other NGOs, uses HOT Tasking Manager. The University of Heidelberg hosts the Disastermappers Project for training university students in mapping for humanitarian purposes. When Ebola broke out in 2014, the volunteers mapped 100,000 buildings and hundreds of miles of roads in Guinea in just five days.

Software

OSM application architectural components
OSM application architectural components

OpenStreetMap applications utilize multiple components to provide services. The map data is rendered using pre-generated tiles for various levels of zoom. Editing applications typically support display of imagery, and field mapping data in the form of GPS traces and voice, photo, video annotations to aid in editing map.

OsmAnd, Locus Map, Maps.me, and Organic Maps are some of the mobile applications for general public use. Some of these also support editing OSM.

Map renderers

OpenStreetMap of Soho, central London, shown in the "Carto" OpenStreetMap layer
Raw OpenStreetMap data of India loading in QGIS for analysis and map-making

The official OpenStreetMap website provides a slippy map interface based on the Leaflet JavaScript library (and formerly built on OpenLayers), displaying map tiles rendered by the Mapnik rendering engine. The basic map views offered are Standard, Cycle map, Transport map and Humanitarian. The website uses Ruby on Rails to enable users to edit maps and view changesets. The application interfaces with OSM PostgreSQL database for storage of user data and edit metadata. The default map is rendered by Mapnik, stored in PostGIS, and powered by an Apache module called mod_tile.

Editors

The map data can be edited from a number of editing appliations, utilising satellite/aerial imagery, GPS traces, and local knowledge. JOSM, iD, StreetComplete, Rapid, and Potlatch are the top 5 editing tools for contributions during 2018–2023 according to a study by the Heidelberg Institute for Geoinformation Technology.

iD is used for editing on the OSM website. It was originally developed by Mapbox, with initial financing from the Knight Foundation and is available under open source. "RapiD" is a web based editor derived from iD. It is developed and used by Facebook for "map with ai" project to add artificial intelligence (AI) detected maps of roads to OSM. JOSM, Potlatch, and Merkaartor are more powerful desktop editing applications that are better suited for advanced users.

A map with different colored icons on it, currently a quest about a house number
StreetComplete asking user a question. User filled in the answer. After tapping "OK" this answer will be added to an OpenStreetMap database.

Vespucci is the primary full-featured editor for Android; it has been regularly released since 2009. StreetComplete, an Android app launched in 2016, allows users without any OpenStreetMap knowledge to answer simple questions for existing data in OpenStreetMap, and thus contribute data.

Search and analysis tools

A geocoder indexes map data so that users can search it by name and address (geocoding) or look up an address based on a given coordinate pair (reverse geocoding). Several geocoders are designed to index OSM data, including Nominatim (from the Latin, 'by name'), which is built into the official OSM website along with GeoNames. Komoot's Photon search engine provides incremental search functionality based on a Nominatim database.

The Overpass API searches the OSM database for features whose metadata or topology match criteria specified in a structured query language. QLever is a triplestore that accepts standard SPARQL queries to return facts about the OSM database. Heidelberg University has developed a geographic information retrieval system that answers natural language queries based on OSM data.

Route planners

A variety of route planning libraries and services are based on OpenStreetMap data. OpenStreetMap's official website has featured GraphHopper, the Open Source Routing Machine, and Valhalla since February 2015. Mobile applications such as CycleStreets, Komoot, Maps.me, Organic Maps, and OsmAnd also provide offline route planning capabilities.

Quality assurance

As OSM is a crowd sourced project with complex tagging scheme, there is potential for introduction of unintentional errors and intentional errors. Contributors use history menu on the OSM website, tools like OSMcha, OSM Inspector and Osmose to monitor, review and fix errors.

OpenStreetMap data has been favourably compared with proprietary datasources, although as of 2009 data quality varied across the world. A study in 2011 compared OSM data with TomTom for Germany. For car navigation TomTom has 9% more information, while for the entire street network, OSM has 27% more information.

OSM community

Humanitarian aid

OpenStreetMap Philippines GPS map, an end-product of over a thousand crisis mappers that contributed almost 5 million map updates during the 2013 Haiyan humanitarian activation

The 2010 Haiti earthquake established a model for non-governmental organisations (NGOs) to collaborate with international organisations. OpenStreetMap and Crisis Commons volunteers used available satellite imagery to map the roads, buildings and refugee camps of Port-au-Prince in just two days, building "the most complete digital map of Haiti's roads". The resulting data and maps have been used by several organisations providing relief aid, such as the World Bank, the European Commission Joint Research Centre, the Office for the Coordination of Humanitarian Affairs, UNOSAT and others.

After Haiti, the OpenStreetMap community continued mapping to support humanitarian organisations for various crises and disasters. After the Northern Mali conflict (January 2013), Typhoon Haiyan in the Philippines (November 2013), and the Ebola virus epidemic in West Africa (March 2014), the OpenStreetMap community in association with the NGO Humanitarian OpenStreetMap Team (HOT) has shown it can play a significant role in supporting humanitarian organisations.

Derivative map projects

Several open collaborative mapping projects integrate with the OpenStreetMap database or are otherwise affiliated with the OpenStreetMap project:

  • OpenHistoricalMap (OHM) is a world historical map based on the OpenStreetMap software platform.
  • OpenRailwayMap (ORM) is a detailed online map of the world's railway infrastructure, built on OpenStreetMap data. It has been available since mid-2013 at openrailwaymap.org.
  • OpenSeaMap is a world nautical chart built as a mashup of OpenStreetMap, crowdsourced water depth tracks, and third-party weather and bathymetric data.
  • Wheelmap.org is a portal for mapping, browsing, and reviewing wheelchair-accessible places.

OSM based companies

Mapbox is one of the earliest companies to provide OSM based services. Custom maps can also be generated from OpenStreetMap data through various software including Jawg Maps, Mapnik, Mapbox Studio, Mapzen's Tangrams. OSRM, GraphHopper, MapQuest and Mapbox's Valhalla are some of the route planning application providers.

"State of the Map" conferences

Since 2007, the OpenStreetMap community has held an annual, international conference called State of the Map (SotM) where all stake holders gather to share progress and discuss issues. There are also various national, regional and continental SotM conferences, such as SotM U.S., SotM Baltics, SotM Asia & SotM Africa.

Organisations using OSM

Wikimedia projects provide locator map for cities and travel points of interest based on OpenStreetMap data. Wikipedia uses OpenStreetMap data to render custom maps using the Kartographer extension.

A variety of popular services incorporate some sort of geolocation or map-based component. Notable services using OpenStreetMap for this include Facebook, Apple Inc., Craigslist, Flickr, Foursquare, Snapchat, Strava, and Grab.

Navigation users include Amazon, Tesla, Garmin, Moovit, Organic Maps, Geotab, Komoot, and Gurtam.

Game developer users include Ballardia (World of the Living Dead: Resurrection), Niantic (Ingress, Pokémon Go), Hasbro (Monopoly City Streets), and Jutsu Games (Infection Free Zone).

Some innovative applications include Webots; creating a virtual environment for autonomous vehicle simulations and OpenTopoMap rendering topographic maps based on OpenStreetMap and SRTM data.

Meta (then Facebook) released the Daylight Map Distribution in 2020, intended as a validated and enhanced data release that companies could use in production. In May 2024, Daylight was sunsetted and superseded by the Overture Maps Foundation.

The Overture Maps Foundation was launched in late 2022, and also provides enhanced data releases. It encourages its contributors to contribute to OSM.

Some public transportation providers rely on OpenStreetMap data in their route planning services and for other analysis needs. In 2011, TriMet, which serves the Portland, Oregon, metropolitan area, found that OpenStreetMap's street data, consumed through the routing engine OpenTripPlanner and the search engine Apache Solr, yields better results than analogous GIS datasets managed by local government agencies.

OSM based research

OpenStreetMap data is used in scientific studies. For example, road data was used for research of remaining roadless areas and in the creation of the annual Forest Landscape Integrity Index.

Global mental health

From Wikipedia, the free encyclopedia

Global mental health is the international perspective on different aspects of mental health. It is 'the area of study, research and practice that places a priority on improving mental health and achieving equity in mental health for all people worldwide'. There is a growing body of criticism of the global mental health movement, and has been widely criticised as a neo-colonial or "missionary" project and as primarily a front for pharmaceutical companies seeking new clients for psychiatric drugs.

In theory, taking into account cultural differences and country-specific conditions, it deals with the epidemiology of mental disorders in different countries, their treatment options, mental health education, political and financial aspects, the structure of mental health care systems, human resources in mental health, and human rights issues among others.

The overall aim of the field of global mental health is to strengthen mental health all over the world by providing information about the mental health situation in all countries, and identifying mental health care needs in order to develop cost-effective interventions to meet those specific needs.

The global burden of disease

Disability-adjusted life year for neuropsychiatric conditions per 100,000 inhabitants in 2002:
  no data
  less than 10
  10–20
  20–30
  30–40
  40–50
  50–60
  60–80
  80–100
  100–120
  120–140
  140–150
  more than 150

Mental, neurological, and substance use disorders make a substantial contribution to the global burden of disease (GBD). This is a global measure of so-called disability-adjusted life years (DALY's) assigned to a certain disease/disorder, which is a sum of the years lived with disability and years of life lost due to this disease within the total population. Neuropsychiatric conditions account for 14% of the global burden of disease. Among non-communicable diseases, they account for 28% of the DALY's – more than cardiovascular disease or cancer. However, it is estimated that the real contribution of mental disorders to the global burden of disease is even higher, due to the complex interactions and co-morbidity of physical and mental illness.

Around the world, almost one million people die due to suicide every year, and it is the third leading cause of death among young people. The most important causes of disability due to health-related conditions worldwide include unipolar depression, alcoholism, schizophrenia, bipolar depression and dementia. In low- and middle-income countries, these conditions represent a total of 19.1% of all disability related to health conditions.

According to Paul and Moser’s meta-analysis, countries with high income inequality and poor unemployment protections have worse mental health outcomes among the unemployed.

Mental health by country

Africa

Mental illnesses and mental health disorders are widespread concerns among underdeveloped African countries, yet these issues are largely neglected, as mental health care in Africa is given statistically less attention than it is in other, westernized nations. Rising death tolls due to mental illness demonstrate the imperative need for improved mental health care policies and advances in treatment for Africans suffering from psychological disorders.

Underdeveloped African countries are so visibly troubled by physical illnesses, disease, malnutrition, and contamination that the dilemma of lacking mental health care has not been prioritized, makes it challenging to have a recognized impact on the African population. In 1988 and 1990, two original resolutions were implemented by the World Health Organization's Member States in Africa. AFR/RC39/R1 and AFR/RC40/R9 attempted to improve the status of mental health care in specific African regions to combat its growing effects on the African people. However, it was found that these new policies had little impact on the status of mental health in Africa, ultimately resulting in an incline in psychological disorders instead of the desired decline, and causing this to seem like an impossible problem to manage.

In Africa, many socio-cultural and biological factors have led to heightened psychological struggles, while also masking their immediate level of importance to the African eye. Increasing rates of unemployment, violence, crime, rape, and disease are often linked to substance abuse, which can cause mental illness rates to inflate. Additionally, physical disease like HIV/AIDS, the Ebola epidemic, and malaria often have lasting psychological effects on victims that go unrecognized in African communities because of their inherent cultural beliefs. Traditional African beliefs have led to the perception of mental illness as being caused by supernatural forces, preventing helpful or rational responses to abnormal behavior. For example, Ebola received loads of media attention when it became rampant in Africa and eventually spread to the US, however, researchers never really paid attention to its psychological effects on the African brain. Extreme anxiety, struggles with grief, feelings of rejection and incompetence, depression leading to suicide, PTSD, and much more are only some of the noted effects of diseases like Ebola. These epidemics come and go, but their lasting effects on mental health are remaining for years to come, and even ending lives because of the lack of action. There has been some effort to financially fund psychiatric support in countries like Liberia, due to its dramatic mental health crisis after warfare, but not much was benefited. Aside from financial reasons, it is so difficult to enforce mental health interventions and manage mental health in general in underdeveloped countries simply because the individuals living there do not necessarily believe in western psychiatry. It is also important to note that the socio-cultural model of psychology and abnormal behavior is dependent on factors surrounding cultural differences. This causes mental health abnormalities to remain more hidden due to the culture's natural behavior, compared to westernized behavior and cultural norms.

This relationship between mental and physical illness is an ongoing cycle that has yet to be broken. While many organizations are attempting to solve problems about physical health in Africa, as these problems are clearly visible and recognizable, there is little action taken to confront the underlying mental effects that are left on the victims. It is recognized that many of the mentally ill in Africa search for help from spiritual or religious leaders, however this is widely because many African countries are significantly lacking in mental health professionals in comparison to the rest of the world. In Ethiopia alone, there are “only 10 psychiatrists for the population of 61 million people,” studies have shown. While numbers have definitely changed since this research was done, the lack of psychological professionals throughout African continues with a current average of 1.4 mental health workers per 100,000 people compared to the global statistic of 9.0 professionals per 100,000 people. Additionally, statistics show that the “global annual rate of visits to mental health outpatient facilities is 1,051 per 100,000 population,” while “in Africa the rate is 14 per 100,000” visits. About half of Africa's countries have some sort of mental health policy, however, these policies are highly disregarded, as Africa's government spends “less than 1% of the total health budget on mental health”. Specifically in Sierra Leone, about 98.8% of people suffering from mental disorders remain untreated, even after the building of a well below average psychiatric hospital, further demonstrating the need for intervention.

Not only has there been little hands-on action taken to combat mental health issues in Africa, but there has also been little research done on the topic to spread its awareness and prevent deaths. The Lancet Global Health acknowledges that there are well over 1,000 published articles covering physical health in Africa, but there are still less than 50 discussing mental health. And this pressing dilemma of prioritizing physical health vs. mental health is only worsening as the continent's population is substantially growing with research showing that “Between 2000 and 2015 the continent's population grew by 49%, yet the number of years lost to disability as a result of mental and substance use disorders increased by 52%”. The number of deaths caused by mental instability is truly competing with those caused by physical diseases: “In 2015, 17.9 million years were lost to disability as a consequence of mental health problems. Such disorders were almost as important a cause of years lost to disability as were infectious and parasitic diseases, which accounted for 18.5 million years lost to disability,”. Mental health and physical health care, while they may seem separate, are very much connected, as these two factors determine life or death for humans. As new challenges surface and old challenges still haven't been prioritized, Africa's mental health care policies need significant improvement in order to provide its people with the appropriate health care they deserve, hopefully preventing this problem from expanding.

Australia

A survey conducted by Australian Bureau of Statistics in 2008 regarding adults with manageable to severe neurosis reveals almost half of the population had a mental disorder at some point of their life and one in five people had a sustained disorder in the preceding 12 months. In neurotic disorders, 14% of the population experienced anxiety and comorbidity disorders were next to common mental disorder with vulnerability to substance abuse and relapses. There were distinct gender differences in disposition to mental health illness. Women were found to have high rate of mental health disorders, and Men had higher propensity of risk for substance abuse. The SMHWB survey showed families that had low socioeconomic status and high dysfunctional patterns had a greater proportional risk for mental health disorders. A 2010 survey regarding adults with psychosis revealed 5 persons per 1000 in the population seeks professional mental health services for psychotic disorders and the most common psychotic disorder was schizophrenia.

Bangladesh

Mental health disorder is considered a major public health concern and it constitutes about 13% of the Global Burden of disease and severe mental health disease may reduce each individual's life expectancy by about 20%. Low and middle-income countries have a higher burden of mental health disorder as it is not considered as a health problem as other chronic diseases. Being a low-income country, in Bangladesh, mental health issues are highly stigmatized.

A community-based study in the rural area of Bangladesh in 2000-2001 estimated that the burden of mental morbidity was 16.5% among rural people and most were suffering from mainly depression and anxiety and which was one-half and one-third of total cases respectively. Furthermore, the prevalence of mental disorders was higher in women in large families aged 45 years.

Care for mental health in Bangladesh

A study conducted in 2008 stated that only 16% of patients came directly to the Mental Health Practitioner with a mean delay of 10.5 months of the onset of mental illness, which made them more vulnerable in many ways. 22% of patients went for the religious or traditional healer and 12% consulted a rural medical practitioner with the least delay of 2-2.5 weeks.

Canada

According to statistics released by the Centre of Addiction and Mental Health one in five people in Canada experience a mental health or addiction problem. Young people of ages 15 to 25 are particularly found to be vulnerable. Major depression is found to affect 8% and anxiety disorder 12% of the population. Women are 1.5 times more likely to suffer from mood and anxiety disorders. WHO points out that there are distinct gender differences in patterns of mental health and illness. The lack of power and control over their socioeconomic status, gender based violence; low social position and responsibility for the care of others render women vulnerable to mental health risks. Since more women than men seek help regarding a mental health problem, this has led to not only gender stereotyping but also reinforcing social stigma. WHO has found that this stereotyping has led doctors to diagnose depression more often in women than in men even when they display identical symptoms. Often communication between health care providers and women is authoritarian leading to either the under-treatment or over-treatment of these women.

Women's College Hospital has a program called the "Women's Mental Health Program" where doctors and nurses help treat and educate women regarding mental health collaboratively, individually, and online by answering questions from the public.

Another Canadian organization serving mental health needs is the Centre for Addiction and Mental Health (CAMH). CAMH is one of Canada's largest and most well-known health and addiction facilities, and it has received international recognitions from the Pan American Health Organization and World Health Organization Collaborating Centre. They do research in areas of addiction and mental health in both men and women. In order to help both men and women, CAMH provides "clinical care, research, education, policy development and health promotion to help transform the lives of people affected by mental health and addiction issues." CAMH is different from Women's College Hospital due to its widely known rehab centre for women who have minor addiction issues, to severe ones. This organization provides care for mental health issues by assessments, interventions, residential programs, treatments, and doctor and family support.

Middle East

Israel

In Israel, a Mental Health Insurance Reform took effect in July 2015, transferring responsibility for the provision of mental health services from the Ministry of Health to the four national health plans. Physical and mental health care were united under one roof; previously they had functioned separately in terms of finance, location, and provider. Under the reform, the health plans developed new services or expanded existing ones to address mental health problems.

United States

According to the World Health Organization in 2004, depression is the leading cause of disability in the United States for individuals ages 15 to 44. Absence from work in the U.S. due to depression is estimated to be in excess of $31 billion per year. Depression frequently co-occurs with a variety of medical illnesses such as heart disease, cancer, and chronic pain and is associated with poorer health status and prognosis. Each year, roughly 30,000 Americans take their lives, while hundreds of thousands make suicide attempts (Centers for Disease Control and Prevention). In 2004, suicide was the 11'th leading cause of death in the United States (Centers for Disease Control and Prevention), third among individuals ages 15–24. Despite the increasingly availability of effectual depression treatment, the level of unmet need for treatment remains high.  By way of comparison, a study conducted in Australia during 2006 to 2007 reported that one-third (34.9%) of patients diagnosed with a mental health disorder had presented to medical health services for treatment. The US has a shortage of mental healthcare workers, contributing to the unmet need for treatment. By 2025, the US will need an additional 15,400 psychiatrists and 57,490 psychologists to meet the demand for treatment.

Treatment gap

It is estimated that one in four people in the world will be affected by mental or neurological disorders at some point in their lives. Although many effective interventions for the treatment of mental disorders are known, and awareness of the need for treatment of people with mental disorders has risen, the proportion of those who need mental health care but who do not receive it remains very high. This so-called "treatment gap" is estimated to reach between 76–85% for low- and middle-income countries, and 35–50% for high-income countries. According to the National Alliance on Mental Illness, 33.5% of U.S. adults with a serious mental illness and 53.8% of U.S. adults with a mental illness received no treatment for it in the year 2020.

Despite the acknowledged need, for the most part there have not been substantial changes in mental health care delivery during the past years. Main reasons for this problem are public health priorities, lack of a mental health policy and legislation in many countries, a lack of resources – financial and human resources – as well as inefficient resource allocation.

In 2011, the World Health Organization estimated a shortage of 1.18 million mental health professionals, including 55,000 psychiatrists, 628,000 nurses in mental health settings, and 493,000 psychosocial care providers needed to treat mental disorders in 144 low- and middle-income countries. The annual wage bill to remove this health workforce shortage was estimated at about US$4.4 billion.

Interventions

Information and evidence about cost-effective interventions to provide better mental health care are available. Although most of the research (80%) has been carried out in high-income countries, there is also strong evidence from low- and middle-income countries that pharmacological and psychosocial interventions are effective ways to treat mental disorders, with the strongest evidence for depression, schizophrenia, bipolar disorder and hazardous alcohol use.

Recommendations to strengthen mental health systems around the world have been first mentioned in the WHO's World Health Report 2001, which focused on mental health:

  1. Provide treatment in primary care
  2. Make psychotropic drugs available
  3. Give care in the community
  4. Educate the public
  5. Involve communities, families and consumers
  6. Establish national policies, programs and legislation
  7. Develop human resources
  8. Link with other sectors
  9. Monitor community mental health
  10. Support more research

Based on the data of 12 countries, assessed by the WHO Assessment Instrument for Mental Health Systems (WHO-AIMS), the costs of scaling up mental health services by providing a core treatment package for schizophrenia, bipolar affective disorder, depressive episodes and hazardous alcohol use have been estimated. Structural changes in mental health systems according to the WHO recommendations have been taken into account.

For most countries, this model suggests an initial period of investment of US$0.30 – 0.50 per person per year. The total expenditure on mental health would have to rise at least ten-fold in low-income countries. In those countries, additional financial resources will be needed, while in middle- and high-income countries the main challenge will be the reallocation of resources within the health system to provide better mental health service.

Telemental health

In low- and middle income countries there is an increasing demand for telepsychiatry which means offering mental health services through telecommunications technology (mostly videoconferencing and phone calls). This is especially pronounced due to the lack of access to quality healthcare, underfunding and low awareness of mental health issues. In a global health context telemental health may offer access to high-quality mental health services for a wider range of people. At the same time there are concerns around data security and challenges regarding proper infrastructure, capacity, access and skills.

Prevention

Prevention is beginning to appear in mental health strategies, including the 2004 WHO report "Prevention of Mental Disorders", the 2008 EU "Pact for Mental Health" and the 2011 US National Prevention Strategy. NIMH or the National Institute of Mental Health has over 400 grants.

Should you have experienced four or more adverse childhood experiences, you're 3.2 to 4.0 times more likely to suffer from depression, as well as from various other health problems.

Campaigns

There are many different campaigns that are being run around the world that are trying to help all people with their mental health.  Here some examples of campaigns around the world, from high-level stakeholders:

The Power of Okay is a campaign that is run by a government’s funded company in Scotland called “See Me”. This campaign is mainly focused on mental health in the workplace. It touches on two sides of the system. One being the individual struggling with mental health and not knowing how, or if they should tell anyone. Two being a staff member seeing their colleague struggling, but not knowing how to bring it up, or being worried about saying the wrong thing. This campaign was made to encourage people to reach out to their colleagues, family members, friends, neighbors, and ask the question, "are you okay?"

Not Myself Today is another campaign that has started and is run in Canada, connected with the European Brain Council (EBC). This campaign is more focused on helping mental health in a workplace setting. It is trying to help companies raise awareness, reduce stigma, and build a supportive community. Not Myself Today is a program that any company can get registered for online. Once registered the company will get a comprehensive Not Myself Today toolkit and member online access. You then can engage in the provided material and evaluation surveys, which help see how the program is impacting your workplace.

Better Health-Every Mind Matters is a campaign that is commissioned by Public Health England (PHE). With this campaign PHE is trying to bring to light the struggles and difficulties that have come after COVID-19. This campaign's goal is to support people to take action to look after their mental health and wellbeing, and to also help support those that are around them. The PHE encourages people to get a free NHS approved mind plan. This can be done by answering five questions through Every Mind Matters website. After answering these questions, you will get a personalized plan with tips to help you with what you are currently struggling with.    

Stop The Stigma is a campaign that was started by the Canadian Mental Health association (CAMH). With this campaign CAMH came out with some ads of people talking in their workplace. These ads would have someone of a higher status, like a manager or a boss talking about their employees who had cancer. Instead of talking about it in a sincere and sympathetic way, they would talk about it in the way that most people talk about mental health. They would use phrases like, “Is it just a made-up illness to get out of work?” or “Just take something, stuck it up and get back to work.” This just shows how insincere people can be about mental health and puts in perspective that things need to change.    

The world health organization (WHO) teamed up with United for Global Mental Health and the World Federation of Mental Health and are campaigning for World Mental Health Day (10 October). With this campaign WHO is looking to host a global online advocacy event on mental health. The United for Global Mental Health group also wants to have a 24-hour march for mental health that has livestreamed content from experts that talk about ways to increase awareness and break down the stigma around mental health.

Stakeholders

World Health Organization (WHO)

Two of WHO's core programmes for mental health are WHO MIND (Mental health improvements for Nations Development) and Mental Health Gap Action Programme (mhGAP).

WHO MIND focuses on 5 areas of action to ensure concrete changes in people's daily lives. These are:

  1. Action in and support to countries to improve mental health, such as the WHO Pacific Island Mental Health network (PIMHnet)
  2. Mental health policy, planning and service development
  3. Mental health human rights and legislation
  4. Mental health as a core part of human development
  5. The QualityRights Project which works to unite and empower people to improve the quality of care and promote human rights in mental health facilities and social care homes.

Mental Health Gap Action Programme (mhGAP) is WHO’s action plan to scale up services for mental, neurological and substance use disorders for countries especially with low and lower middle incomes. The aim of mhGAP is to build partnerships for collective action and to reinforce the commitment of governments, international organizations and other stakeholders.

The mhGAP Intervention Guide (mhGAP-IG) was launched in October 2010. It is a technical tool for the management of mental, neurological and substance use disorders in non-specialist health settings. The priority conditions included are: depression, psychosis, bipolar disorders, epilepsy, developmental and behavioural disorders in children and adolescents, dementia, alcohol use disorders, drug use disorders, self-harm/suicide and other significant emotional or medically unexplained complaints.

Criticism

One of the most prominent critics of the Movement for Global Mental Health has been China Mills, author of the book Decolonizing Global Mental Health: The Psychiatrization of the Majority World.

Mills writes that:

This book charts the creeping of psychology and psychiatry across the borders of everyday experience and across geographical borders, as a form of colonialism that comes from within and from outside, swallowed in the form of a pill. It maps an anxious space where socio-economic crises come to be reconfigured as individual crisis – as 'mental illness'; and how potentially violent interventions come to be seen as 'essential' treatment.

Another prominent critic is Ethan Watters, author of Crazy Like Us: The Globalization of the American Psyche. A more constructive approach is offered by Vincenzo Di Nicola whose article on the Global South as an emergent epistemology creates a bridge between critiques of globalization and the initial gaps and limitations of the Global Mental Health movement.

A recent review presents a simple summary outlining the key characteristics of the global mental health landscape and indicating the diversity within the field. This review demonstrates how global mental health is not confined to the local-global debate, which has historically defined it.

Mental health in the Middle East

The study of mental health in the Middle East is an area of research that continues to grow in its scope and content. As of May 10, 2019, WHO study shows over 70 countries and territories across six regions, including Egypt, Iraq, Jordan, Lebanon, the occupied Palestinian territory, Qatar, Syria, Tunisia, the UAE, and Yemen, have prioritized coverage of mental health conditions.

To accurately evaluate and understand the mental health issues of the Middle East, one must take into account the geographic, historical, cultural, and social influences of that part of the world. While each of the many countries commonly considered part of the "Middle East" is unique, there is a binding ethnic fabric that should be considered. Firstly, the Middle East is the origin of many of the major world religions. Christianity, Judaism and Islam, all began in this region. Of these many religions, Islam has had the most lasting and culturally significant influence on the region, encompassing well over ninety percent (90%) of the population by some measurements. The tenets of the Islamic faith, and its strict purpose, certainly have served as both a guide and a hindrance to the practices' of mental health care providers in the Middle East. There is a conflict between ancient religious teachings and the modern day or "Western world" approach to the issues of mental health.

Historical perspective

Mental health in the Middle East, from Pharaonic times through to the Islamic Renaissance, has a rich and complex history. During Pharaonic times, soma and psyche were terms used to define mental disorders, and such disorders were described as problems of the heart or uterus, as stated in Eber's and Kahoun's Papyri. While mystical culture predominated at that time, mental disorders were treated on a somatic basis. In the Islamic era, those with mental illness were not known to have endured any forms of torture, nor were they ostracized; this was due to the belief that possession by a good Muslim genie was possible.

Islam, the predominant religion in the Middle East, was among the earliest major religions to advocate for sympathy and care toward the mentally ill, absolving them from accountability for their actions. Despite the common association of spiritual possession with Islam, a thematic analysis of Arabic texts and four English translations of the Qu'ran revealed no direct link between spiritual possession and mental disorders in the holy scriptures.

In ancient times, mental health treatments in Middle Eastern countries took various forms. For instance, ancient Iran had distinct medical specialties, including healers focused on the body (tan-pezeshk) and those specializing in the psyche (ravan-pezeshk), which are equivalent to contemporary psychiatrists. The first psychiatric hospital in the Middle East, named In Sina, was established in the Syrian Arab Republic in 1929. The building of another hospital in Aleppo followed in 1956.

Historical records include narratives about Masud Khan, born into a Muslim feudal royalty family in Iran in 1924, who likely suffered from undiagnosed bipolar disorder. Notably, he underwent examination by prominent figures in Western psychoanalysis, such as Anna Freud.

Modern Views

Historical views on mental health still remain prominent in the Middle East as the stigma has not changed even in the modern day. Having insufficient knowledge of mental health can lead to a higher probability of developing somatic symptom disorder. This is particularly evident in conflict-affected areas such as Syria and Palestine, where conditions like depression and stress frequently appear as physical health problems. These symptoms are often dismissed or ignored due to the widespread prevalence of similar challenges within the community. Studies have shown that in the Arab region, people tend to link mental health issues with cultural or religious beliefs. There is a highly prevalent stigma and negative attitude that surrounds mental health disorders, which leads to people not seeking appropriate help. Socially acceptable forms of seeking care are practiced by religious leaders, this method remains to be the most prominent form of seeking help.

Regional Variations

The overall lack of mental health services available across the Middle East is a largely contributing factor to people not seeking help. The impact of mental health varies throughout the Middle East due to some parts facing wars, economic difficulties, and sociopolitical unrest. In these countries, due to the challenges faced by individuals, the most basic needs are not met; therefore, mental health often is not prioritized. Whereas in more developed countries, such as Saudi Arabia, where free health care is provided and people do have access to mental health services as the availability of mental health professionals are widely available. Society's attitude towards mental health plays a substantial role in seeking help, compared to the service availability in developing countries.  Saudi Arabia's Vision 2030, includes expanding its mental health infrastructure, by having more services available to those who need help, as well as, the expansion of medical schools and training on mental health.

Spiritual beliefs and superstitions

The belief in being possessed by supernatural entities such as jinn (demons), seher (magic), or hasad (the "evil eye") is prevalent among Muslims in general and is reportedly more prevalent among women, the elderly, and those with lower levels of education. Although the belief in demonic possession is officially condemned as inconsistent with Islam and its teachings, it persists in Middle Eastern culture. These attributions underscore the intricacies involved in comprehending and addressing mental disorders in Middle Eastern culture, highlighting the importance of culturally-sensitive initiatives to reduce stigma.

Zār

Zār (زار) known as possession by a spirit, is exhibited by some Middle Eastern cultures. Specific ceremonies are performed to placate the zār and relieve the symptoms of the afflicted individual. These ritualized ceremonies, organized and facilitated by a leader, include the affected individual and a person previously affected by the zār, and involve "incense, music, and movement". The details of the ceremony vary by region. Some leaders may recommend that the patient first seek the help of a doctor, while others believe that interventions by the doctor, such as using needles for injections, may further agitate the zār, creating more problems for the patient. Those who choose traditional treatment for zār remain in isolation for up to seven days. This syndrome has been reported in North African and Middle Eastern countries, including Ethiopia, Egypt, Iran, and Sudan. Signs and symptoms of zār may include dissociative episodes, unexpected laughing, yelling, or singing, or even patients hitting their heads against a wall. Clients may exhibit apathy and be reclusive. Those under the influence of the zār may refuse to eat or carry out activities of daily living, and may develop an extended interaction with the possessing spirit.

The evil eye

A Corundum Evil Eye Amulet from Mesapotamia ʘDanieliness

The "evil eye" is also known as ʿayn al-ḥasūd (عين الحسود)" and is a belief that certain individuals have the power to cause harm or bad luck to others through their gaze. This belief is found in various cultures around the world, including the Middle East, Mediterranean, South Asia, and Latin America. Excessive fear of the evil eye and those who cast it is common among certain people. Such beliefs serve to benefit charlatans who prey on the minds of such victims. A certain class of society are seen standing at the gates of these charlatans, driven by illusion, disillusion and fear of the evil eye and those who cast it – and the devil whispers to them, leading them to believe that their mental disorders are caused by the evil eye while they benefit from exploiting them. Protective talismans and amulets, known as "nazar" or "evil eye charms", are commonly used in Middle Eastern cultures to ward off the effects of the evil eye. These talismans typically feature an eye symbol, often in blue or turquoise, believed to deflect negative energy.

Traditional and spiritual treatment

According to Ibn Sina, Islamic medicine treats mental illness as a somatic ailment, employing various treatments such as baths, massage, bloodletting, leeches, cupping, cautery, music, and drug therapies involving purgatives, emetics, and opium. In addition to addressing mental illness as a bodily condition, there is a widespread belief in the supernatural origins of madness. Individuals often turn to charms and amulets to protect against jinn, the evil eye, and black magic. Exorcisms, conducted by certain holy men, also known as Shaykhs, are prevalent, particularly among the Sufis. Notably, many patients seek treatment in both the medical and spiritual domains. In Saudi Arabia and other countries in the Gulf region, it is common to consult faith healers or Shaykhs before seeking professional healthcare.

Comparing Western and Middle Eastern Approaches to Mental Health

A comparative study on attitudes toward auditory hallucinations in Saudi Arabia and the United Kingdom revealed significant differences. In Saudi Arabia, some attributed such symptoms to Satan or demons, while others linked them to brain damage or stress. Similarly, in the UK, these attitudes were present, but there was a greater emphasis on stress as a causative factor. Regarding treatment preferences, a majority of Saudis leaned towards religious intervention, while others considered psychological therapy or medication. In the UK, there was a more diverse endorsement of psychological therapy and medication.

Known syndromes

Post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is, unfortunately, common in the Middle East due to the myriad conflicts experienced by people in the region. Diagnostic symptoms for PTSD include recurrent experiencing of the initial traumatic event(s) through flashbacks or recurrent night sweats and nightmares. Those afflicted with post-traumatic stress syndrome often seek to avoid others as well as any stimulus similar to the traumatic occurrence. They may also exhibit increased arousal. Difficulty in falling or staying asleep, unexpected episodic fits of anger, and hypervigilance may also occur. The formal diagnostic criteria for both the DSM-IV-TR and ICD-10) indicate that symptoms last for more than one month and cause significant impairment in social, occupational, and/or other important areas of functioning. There is also some evidence that children suffering from PTSD in the Middle East may experience accelerated aging.

Depression

Depression in the Middle East has been specifically studied at Namazi Hospital Shiraz, in Iran. In a 2006 study of nurses, depressive symptoms were seen in 26.9% of the individuals studied. In this cross-sectional survey, the rate of depression in 130 nurses was investigated using the 21-item Beck Depression Inventory. Data collection also involved individual interviews and follow-up by the research team. Depression has also been found to occur after enduring horrific situations such as war. Witnessing and experiencing such situations creates a sense of hopelessness which develops into depression.

Different causes

In the Middle East, there is a tendency to attribute mental disorders to divine origins. This practice predates Islam and has historical roots in Arabia, Biblical periods, and Ancient Greece. The historical lack of understanding of insanity led to the use of supernatural explanations. Mental health stigma may also arise from a primitive fear of the unseen, particularly because individuals with mental disorders may not exhibit visible symptoms. The unknown nature of mental health illnesses contributes to heightened fear and stigma. Despite scientific data categorizing mental diseases as psychological or physical, supernatural interpretations persist in the Middle East.

Various factors contribute to mental health issues in the region, including sociopolitical unrest, economic challenges, and the transitional phase into adulthood. Instances of wars, mass protests, regime changes, and political instability create an atmosphere of insecurity and economic stagnation, elevating the risk of depression among young adults. Notably, in 2019, Palestine, facing genocide, recorded the highest prevalence, incidence, and DALYs rates of depressive disorders per 100,000 people by age-standardized rate. Demographic shifts in the Middle East, marked by a 'youth bulge,' further complicate the mental health landscape, especially in Egypt. High rates of youth unemployment, particularly among women, have been linked to depression and other mental health challenges.

War

In ongoing war circumstances like Gaza, where the land is under siege, people are unable to experience normal disorders such as PTSD properly. This is because the traumatic instances are continuously occurring and do not apply to the definition of a "post" traumatic disorder. The Palestinian children being treated for mental disorders have a high chance of relapsing due to the ongoing stress and anxiety that surrounds them.

Stigma around mental health

Even though, Islamic principles are established on getting treatment when necessary.  Many in the Middle East continue to view mental issues as God punishing a certain individual. Hardships are perceived as proof that God has a plan for each person, which then leads to people perceiving mental illness as a test from God. Due to religion playing a large role in the Middle East, Muslims often reach out to religious leaders (Imams or Sheikhs) due to their prominent role in society. Due to the implemented importance of other's views, mental health in the Middle East is completely disregarded. An individual could not express their mental issues out of fear of being alienated due to their abnormalness. Children have chosen to struggle silently to prevent bringing shame to their families. Even after experiencing war, refugees from Afghanistan were unable to express their struggles due to the embarrassment that comes with it.

Introduction to entropy

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Introduct...