Physical geography is one of the two major sub-fields of geography. Physical geography is the branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, hydrosphere and geosphere, as opposed to the cultural or built environment, the domain of human geography. Physical Geography can be divided into several sub-fields, as follows: Geomorphology is the field concerned with understanding the surface of the Earth and the processes by which it is shaped, both at the present as well as in the past. Geomorphology as a field has several sub-fields that deal with the specific landforms of various environments e.g. desert geomorphology and fluvial geomorphology. Geomorphology seeks to understand landform history and dynamics, predict future changes through a combination of field observation, physical experiment, numerical modeling. Early studies in geomorphology are the foundation for pedology, one of two main branches of soil science Hydrology is predominantly concerned with the amounts and quality of water moving and accumulating on the land surface and in the soils and rocks near the surface and is typified by the hydrological cycle.
Thus the field encompasses water in rivers, aquifers and to an extent glaciers, in which the field examines the process and dynamics involved in these bodies of water. Hydrology has had an important connection with engineering and has thus developed a quantitative method in its research. Similar to most fields of physical geography it has sub-fields that examine the specific bodies of water or their interaction with other spheres e.g. limnology and ecohydrology. Glaciology is the study of glaciers and ice sheets, or more the cryosphere or ice and phenomena that involve ice. Glaciology groups the latter as continental glaciers and the former as alpine glaciers. Although research in the areas are similar with research undertaken into both the dynamics of ice sheets and glaciers, the former tends to be concerned with the interaction of ice sheets with the present climate and the latter with the impact of glaciers on the landscape. Glaciology has a vast array of sub-fields examining the factors and processes involved in ice sheets and glaciers e.g. snow hydrology and glacial geology.
Biogeography is the science which deals with geographic patterns of species distribution and the processes that result in these patterns. Biogeography emerged as a field of study as a result of the work of Alfred Russel Wallace, although the field prior to the late twentieth century had been viewed as historic in its outlook and descriptive in its approach; the main stimulus for the field since its founding has been that of evolution, plate tectonics and the theory of island biogeography. The field can be divided into five sub-fields: island biogeography, paleobiogeography, phylogeography and phytogeography Climatology is the study of the climate, scientifically defined as weather conditions averaged over a long period of time. Climatology examines both the nature of micro and macro climates and the natural and anthropogenic influences on them; the field is sub-divided into the climates of various regions and the study of specific phenomena or time periods e.g. tropical cyclone rainfall climatology and paleoclimatology.
Meteorology is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and short term forecasting. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the eighteenth century. Meteorological phenomena are observable weather events which illuminate and are explained by the science of meteorology. Pedology is the study of soils in their natural environment, it is one of two main branches of the other being edaphology. Pedology deals with pedogenesis, soil morphology, soil classification. In physical geography pedology is studied due to the numerous interactions between climate, soil life, the mineral materials within soils and its position and effects on the landscape such as lateralization. Palaeogeography is a cross-disciplinary study that examines the preserved material in the stratigraphic record to determine the distribution of the continents through geologic time. All the evidence for the positions of the continents comes from geology in the form of fossils or paleomagnetism.
The use of this data has resulted in evidence for continental drift, plate tectonics, supercontinents. This, in turn, has supported palaeogeographic theories such as the Wilson cycle. Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography and the human geography of the coast, it involves an understanding of coastal weathering processes wave action, sediment movement and weathering, the ways in which humans interact with the coast. Coastal geography, although predominantly geomorphological in its research, is not just concerned with coastal landforms, but the causes and influences of sea level change. Oceanography is the branch of physical geography that studies seas, it covers a wide range including marine organisms and ecosystem dynamics.
OCLC Online Computer Library Center, Incorporated d/b/a OCLC is an American nonprofit cooperative organization "dedicated to the public purposes of furthering access to the world's information and reducing information costs". It was founded in 1967 as the Ohio College Library Center. OCLC and its member libraries cooperatively produce and maintain WorldCat, the largest online public access catalog in the world. OCLC is funded by the fees that libraries have to pay for its services. OCLC maintains the Dewey Decimal Classification system. OCLC began in 1967, as the Ohio College Library Center, through a collaboration of university presidents, vice presidents, library directors who wanted to create a cooperative computerized network for libraries in the state of Ohio; the group first met on July 5, 1967 on the campus of the Ohio State University to sign the articles of incorporation for the nonprofit organization, hired Frederick G. Kilgour, a former Yale University medical school librarian, to design the shared cataloging system.
Kilgour wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library. The plan was to merge the catalogs of Ohio libraries electronically through a computer network and database to streamline operations, control costs, increase efficiency in library management, bringing libraries together to cooperatively keep track of the world's information in order to best serve researchers and scholars; the first library to do online cataloging through OCLC was the Alden Library at Ohio University on August 26, 1971. This was the first online cataloging by any library worldwide. Membership in OCLC is based on use of services and contribution of data. Between 1967 and 1977, OCLC membership was limited to institutions in Ohio, but in 1978, a new governance structure was established that allowed institutions from other states to join. In 2002, the governance structure was again modified to accommodate participation from outside the United States.
As OCLC expanded services in the United States outside Ohio, it relied on establishing strategic partnerships with "networks", organizations that provided training and marketing services. By 2008, there were 15 independent United States regional service providers. OCLC networks played a key role in OCLC governance, with networks electing delegates to serve on the OCLC Members Council. During 2008, OCLC commissioned two studies to look at distribution channels. In early 2009, OCLC negotiated new contracts with the former networks and opened a centralized support center. OCLC provides bibliographic and full-text information to anyone. OCLC and its member libraries cooperatively produce and maintain WorldCat—the OCLC Online Union Catalog, the largest online public access catalog in the world. WorldCat has holding records from private libraries worldwide; the Open WorldCat program, launched in late 2003, exposed a subset of WorldCat records to Web users via popular Internet search and bookselling sites.
In October 2005, the OCLC technical staff began a wiki project, WikiD, allowing readers to add commentary and structured-field information associated with any WorldCat record. WikiD was phased out; the Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988. A browser for books with their Dewey Decimal Classifications was available until July 2013; until August 2009, when it was sold to Backstage Library Works, OCLC owned a preservation microfilm and digitization operation called the OCLC Preservation Service Center, with its principal office in Bethlehem, Pennsylvania. The reference management service QuestionPoint provides libraries with tools to communicate with users; this around-the-clock reference service is provided by a cooperative of participating global libraries. Starting in 1971, OCLC produced catalog cards for members alongside its shared online catalog. OCLC commercially sells software, such as CONTENTdm for managing digital collections.
It offers the bibliographic discovery system WorldCat Discovery, which allows for library patrons to use a single search interface to access an institution's catalog, database subscriptions and more. OCLC has been conducting research for the library community for more than 30 years. In accordance with its mission, OCLC makes its research outcomes known through various publications; these publications, including journal articles, reports and presentations, are available through the organization's website. OCLC Publications – Research articles from various journals including Code4Lib Journal, OCLC Research, Reference & User Services Quarterly, College & Research Libraries News, Art Libraries Journal, National Education Association Newsletter; the most recent publications are displayed first, all archived resources, starting in 1970, are available. Membership Reports – A number of significant reports on topics ranging from virtual reference in libraries to perceptions about library funding. Newsletters – Current and archived newsletters for the library and archive community.
Presentations – Presentations from both guest speakers and OCLC research from conferences and other events. The presentations are organized into five categories: Conference presentations, Dewey presentations, Distinguished Seminar Series, Guest presentations, Research staff
Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century; the 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data, it was not until after the elucidation of the laws of physics and more the development of the computer, allowing for the automated solution of a great many equations that model the weather, in the latter half of the 20th century that significant breakthroughs in weather forecasting were achieved. An important domain of weather forecasting is marine weather forecasting as it relates to maritime and coastal safety, in which weather effects include atmospheric interactions with large bodies of water. Meteorological phenomena are observable weather events that are explained by the science of meteorology.
Meteorological phenomena are described and quantified by the variables of Earth's atmosphere: temperature, air pressure, water vapour, mass flow, the variations and interactions of those variables, how they change over time. Different spatial scales are used to describe and predict weather on local and global levels. Meteorology, atmospheric physics, atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology; the interactions between Earth's atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in many diverse fields such as the military, energy production, transport and construction; the word meteorology is from the Ancient Greek μετέωρος metéōros and -λογία -logia, meaning "the study of things high in the air". The ability to predict rains and floods based on annual cycles was evidently used by humans at least from the time of agricultural settlement if not earlier.
Early approaches to predicting weather were practiced by priests. Cuneiform inscriptions on Babylonian tablets included associations between rain; the Chaldeans differentiated 46 ° halos. Ancient Indian Upanishads contain mentions of seasons; the Samaveda mentions sacrifices to be performed. Varāhamihira's classical work Brihatsamhita, written about 500 AD, provides evidence of weather observation. In 350 BC, Aristotle wrote Meteorology. Aristotle is considered the founder of meteorology. One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle; the book De Mundo noted If the flashing body is set on fire and rushes violently to the Earth it is called a thunderbolt. They are all called ` swooping bolts'. Lightning is sometimes smoky, is called'smoldering lightning". At other times, it travels in crooked lines, is called forked lightning; when it swoops down upon some object it is called'swooping lightning'. The Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs.
The work of Theophrastus remained a dominant influence in the study of weather and in weather forecasting for nearly 2,000 years. In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system. According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat, in which he deals with the application of meteorology to agriculture during the Muslim Agricultural Revolution, he describes the meteorological character of the sky, the planets and constellations, the sun and moon, the lunar phases indicating seasons and rain, the anwa, atmospheric phenomena such as winds, lightning, floods, rivers, lakes. Early attempts at predicting weather were related to prophecy and divining, were sometimes based on astrological ideas. Admiral FitzRoy tried to separate scientific approaches from prophetic ones. Ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations. In 1021, Alhazen showed that atmospheric refraction is responsible for twilight.
St. Albert the Great was the first to propose that each drop of falling rain had the form of a small sphere, that this form meant that the rainbow was produced by light interacting with each raindrop. Roger Bacon was the first to calculate the angular size of the rainbow, he stated. In the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and explained the secondary rainbow. In 1716, Edmund Halley suggested that aurorae are caused by "magnetic effluvia" moving along the Earth's magnetic field lines. In 1441, King Sejong's son, Prince Munjong of Korea, invented the first standardized rain gauge; these were sent throughout the Joseon dynasty of Korea as an official tool to assess land taxes based
Human geography or anthropogeography is the branch of geography that deals with the study of people and their communities, cultures and interactions with the environment by studying their relations with and across space and place. Human geography attends to human patterns of social interaction, as well as spatial level interdependencies, how they influence or affect the earth's environment; as an intellectual discipline, geography is divided into the sub-fields of physical geography and human geography, the latter concentrating upon the study of human activities, by the application of qualitative and quantitative research methods. Geography was not recognized as a formal academic discipline until the 18th century, although many scholars had undertaken geographical scholarship for much longer through cartography; the Royal Geographical Society was founded in England in 1830, although the United Kingdom did not get its first full Chair of geography until 1917. The first real geographical intellect to emerge in United Kingdom's geographical minds was Halford John Mackinder, appointed reader at Oxford University in 1887.
The National Geographic Society was founded in the United States in 1888 and began publication of the National Geographic magazine which became, continues to be, a great popularizer of geographic information. The society has long supported geographic education on geographical topics; the Association of American Geographers was founded in 1904 and was renamed the American Association of Geographers in 2016 to better reflect the international character of its membership. One of the first examples of geographic methods being used for purposes other than to describe and theorize the physical properties of the earth is John Snow's map of the 1854 Broad Street cholera outbreak. Though Snow was a physician and a pioneer of epidemiology rather than a geographer, his map is one of the earliest examples of health geography; the now distinct differences between the subfields of physical and human geography have developed at a date. This connection between both physical and human properties of geography is most apparent in the theory of environmental determinism, made popular in the 19th century by Carl Ritter and others, has close links to the field of evolutionary biology of the time.
Environmental determinism is the theory, that people's physical and moral habits are directly due to the influence of their natural environment. However, by the mid-19th century, environmental determinism was under attack for lacking methodological rigor associated with modern science, as a means to justify racism and imperialism. A similar concern with both human and physical aspects is apparent during the 19th and first half of the 20th centuries focused on regional geography; the goal of regional geography, through something known as regionalisation, was to delineate space into regions and understand and describe the unique characteristics of each region through both human and physical aspects. With links to and cultural ecology some of the same notions of causal effect of the environment on society and culture remain with environmental determinism. By the 1960s, the quantitative revolution led to strong criticism of regional geography. Due to a perceived lack of scientific rigor in an overly descriptive nature of the discipline, a continued separation of geography from its two subfields of physical and human geography and from geology, geographers in the mid-20th century began to apply statistical and mathematical models in order to solve spatial problems.
Much of the development during the quantitative revolution is now apparent in the use of geographic information systems. Well-known geographers from this period are Fred K. Schaefer, Waldo Tobler, William Garrison, Peter Haggett, Richard J. Chorley, William Bunge, Torsten Hägerstrand. From the 1970s, a number of critiques of the positivism now associated with geography emerged. Known under the term'critical geography,' these critiques signaled another turning point in the discipline. Behavioral geography emerged for some time as a means to understand how people made perceived spaces and places, made locational decisions; the more influential ` radical geography' emerged in the 1980s. It draws on Marxist's theory and techniques, is associated with geographers such as David Harvey and Richard Peet. Radical geographers seek to say meaningful things about problems recognized through quantitative methods, provide explanations rather than descriptions, put forward alternatives and solutions, be politically engaged, rather than using the detachment associated with positivists..
Radical geography and the links to Marxism and related theories remain an important part of contemporary human geography. Critical geography saw the introduction of'humanistic geography', associated with the work of Yi-Fu Tuan, which pushed for a much more qualitative approach in methodology; the changes under critical geography have led to contemporary approaches in the discipline such as feminist geography, new cultural geography, "demonic" geographies, the engagement with postmodern and post-structural theories and philosophies. The primary fields of study in human geography focus around the core fields of: Cultural geography is the study of cultural products and norms - their variation across spaces and places, as well as their relations, it focuses on describing and analyzing the ways language, religio
Chicago the City of Chicago, is the most populous city in Illinois, as well as the third most populous city in the United States. With an estimated population of 2,716,450, it is the most populous city in the Midwest. Chicago is the principal city of the Chicago metropolitan area referred to as Chicagoland, the county seat of Cook County, the second most populous county in the United States; the metropolitan area, at nearly 10 million people, is the third-largest in the United States, the fourth largest in North America and the third largest metropolitan area in the world by land area. Located on the shores of freshwater Lake Michigan, Chicago was incorporated as a city in 1837 near a portage between the Great Lakes and the Mississippi River watershed and grew in the mid-nineteenth century. After the Great Chicago Fire of 1871, which destroyed several square miles and left more than 100,000 homeless, the city made a concerted effort to rebuild; the construction boom accelerated population growth throughout the following decades, by 1900 Chicago was the fifth largest city in the world.
Chicago made noted contributions to urban planning and zoning standards, including new construction styles, the development of the City Beautiful Movement, the steel-framed skyscraper. Chicago is an international hub for finance, commerce, technology, telecommunications, transportation, it is the site of the creation of the first standardized futures contracts at the Chicago Board of Trade, which today is the largest and most diverse derivatives market gobally, generating 20% of all volume in commodities and financial futures. O'Hare International Airport is the one of the busiest airports in the world, the region has the largest number of U. S. highways and greatest amount of railroad freight. In 2012, Chicago was listed as an alpha global city by the Globalization and World Cities Research Network, it ranked seventh in the entire world in the 2017 Global Cities Index; the Chicago area has one of the highest gross domestic products in the world, generating $680 billion in 2017. In addition, the city has one of the world's most diversified and balanced economies, not being dependent on any one industry, with no single industry employing more than 14% of the workforce.
Chicago's 58 million domestic and international visitors in 2018, made it the second most visited city in the nation, behind New York City's approximate 65 million visitors. The city ranked first place in the 2018 Time Out City Life Index, a global quality of life survey of 15,000 people in 32 cities. Landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, the Art Institute of Chicago, Museum Campus, the Willis Tower, Grant Park, the Museum of Science and Industry, Lincoln Park Zoo. Chicago's culture includes the visual arts, film, comedy and music jazz, soul, hip-hop and electronic dance music including house music. Of the area's many colleges and universities, the University of Chicago, Northwestern University, the University of Illinois at Chicago are classified as "highest research" doctoral universities. Chicago has professional sports teams in each of the major professional leagues, including two Major League Baseball teams; the name "Chicago" is derived from a French rendering of the indigenous Miami-Illinois word shikaakwa for a wild relative of the onion, known to botanists as Allium tricoccum and known more as ramps.
The first known reference to the site of the current city of Chicago as "Checagou" was by Robert de LaSalle around 1679 in a memoir. Henri Joutel, in his journal of 1688, noted that the eponymous wild "garlic" grew abundantly in the area. According to his diary of late September 1687:...when we arrived at the said place called "Chicagou" which, according to what we were able to learn of it, has taken this name because of the quantity of garlic which grows in the forests in this region. The city has had several nicknames throughout its history such as the Windy City, Chi-Town, Second City, the City of the Big Shoulders, which refers to the city's numerous skyscrapers and high-rises. In the mid-18th century, the area was inhabited by a Native American tribe known as the Potawatomi, who had taken the place of the Miami and Sauk and Fox peoples; the first known non-indigenous permanent settler in Chicago was Jean Baptiste Point du Sable. Du Sable arrived in the 1780s, he is known as the "Founder of Chicago".
In 1795, following the Northwest Indian War, an area, to be part of Chicago was turned over to the United States for a military post by native tribes in accordance with the Treaty of Greenville. In 1803, the United States Army built Fort Dearborn, destroyed in 1812 in the Battle of Fort Dearborn and rebuilt; the Ottawa and Potawatomi tribes had ceded additional land to the United States in the 1816 Treaty of St. Louis; the Potawatomi were forcibly removed from their land after the Treaty of Chicago in 1833. On August 12, 1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 4,000 people. On June 15, 1835, the first public land sales began with Edmund Dick Taylor as U. S. Receiver of Public Monies; the City of Chicago was incorporated on Saturday, March 4, 1837, for several decades was the world's fastest-growing city. As the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States.
Chicago's first railway and Chicago Union Railroad, the Illi
Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a young field, its borders are fluid. There is considerable overlap with the fields of ecology, evolutionary biology, microbiology and biogeochemistry. Geobiology applies the principles and methods of biology and geology to the study of the ancient history of the co-evolution of life and Earth as well as the role of life in the modern world. Geobiologic studies tend to be focused on microorganisms, on the role that life plays in altering the chemical and physical environment of the lithosphere, hydrosphere and/or cryosphere, it differs from biogeochemistry in that the focus is on processes and organisms over space and time rather than on global chemical cycles. Geobiological research synthesizes the geologic record with modern biologic studies, it deals with process - how organisms affect the Earth and vice versa - as well as history - how the Earth and life have changed together.
Much research is grounded in the search for fundamental understanding, but geobiology can be applied, as in the case of microbes that clean up oil spills. Geobiology employs molecular biology, environmental microbiology, chemical analyses, the geologic record to investigate the evolutionary interconnectedness of life and Earth, it attempts to understand how the Earth has changed since the origin of life and what it might have been like along the way. Some definitions of geobiology push the boundaries of this time frame - to understanding the origin of life and to the role that man has played and will continue to play in shaping the Earth in the Anthropocene; the term geobiology was coined by Lourens Baas Becking in 1934. In his words, geobiology "is an attempt to describe the relationship between organisms and the Earth," for "the organism is part of the Earth and its lot is interwoven with that of the Earth." Baas Becking's definition of geobiology was born of a desire to unify environmental biology with laboratory biology.
The way he practiced it aligns with modern environmental microbial ecology, though his definition remains applicable to all of geobiology. In his book, Bass Becking stated that he had no intention of inventing a new field of study. Baas Becking's understanding of geobiology was influenced by his predecessors, including Martinus Beyerinck, his teacher from the Dutch School of Microbiology. Others included Vladimir Vernadsky, who argued that life changes the surface environment of Earth in The Biosphere, his 1926 book, Sergei Vinogradsky, famous for discovering lithotrophic bacteria; the first laboratory dedicated to the study of geobiology was the Baas Becking Geobiological Laboratory in Australia, which opened its doors in 1965. However, it took another 40 or so years for geobiology to become a rooted scientific discipline, thanks in part to advances in geochemistry and genetics that enabled scientists to begin to synthesize the study of life and planet. In the 1930s, Alfred Treibs discovered chlorophyll-like porphyrins in petroleum, confirming its biological origin, thereby founding organic geochemistry and establishing the notion of biomarkers, a critical aspect of geobiology.
But several decades passed before the tools were available to begin to search in earnest for chemical marks of life in the rocks. In the 1970s and'80s, scientists like Geoffrey Eglington and Roger Summons began to find lipid biomarkers in the rock record using equipment like GCMS. On the biology side of things, in 1977, Carl Woese and George Fox published a phylogeny of life on Earth, including a new domain - the Archaea, and in the 1990s, genetics and genomics studies became possible, broadening the scope of investigation of the interaction of life and planet. Today, geobiology has its own journals, such as Geobiology, established in 2003, Biogeosciences, established in 2004, as well as recognition at major scientific conferences, it got its own Gordon Research Conference in 2011, a number of geobiology textbooks have been published, many universities around the world offer degree programs in geobiology. The most profound geobiological event is the introduction of oxygen into the atmosphere by photosynthetic bacteria.
This oxygenation of Earth's primoidial atmosphere and the oxygenation of the oceans altered surface biogeochemical cycles and the types of organisms that have been evolutionarily selected for. A subsequent major change was the advent of multicellularity; the presence of oxygen allowed eukaryotes and multicellular life to evolve. More anthropocentric geobiologic events include the origin of animals and the establishment of terrestrial plant life, which affected continental erosion and nutrient cycling, changed the types of rivers observed, allowing channelization of what were predominantly braided rivers. More subtle geobiological events include the role of termites in overturning sediments, coral reefs in depositing calcium carbonate and breaking waves, sponges in absorbing dissolved marine silica, the role of dinosaurs in breaching river levees and promoting flooding, the role of large mammal dung in distributing nutrients. Geobiology is founded upon a few core concepts that unite the study of life.
While there are many aspects of studying past and present interactions between life and Earth that are unclear, several important ideas and concepts provide a basis of knowledge in geobiology that serve as a platform for posing researchable questions, including the evolution of life and planet and the co-evolution of the two, genetics - from both a historical and functional standpoint, the metabolic diversity of all life
Spatial analysis or spatial statistics includes any of the formal techniques which study entities using their topological, geometric, or geographic properties. Spatial analysis includes a variety of techniques, many still in their early development, using different analytic approaches and applied in fields as diverse as astronomy, with its studies of the placement of galaxies in the cosmos, to chip fabrication engineering, with its use of "place and route" algorithms to build complex wiring structures. In a more restricted sense, spatial analysis is the technique applied to structures at the human scale, most notably in the analysis of geographic data. Complex issues arise in spatial analysis, many of which are neither defined nor resolved, but form the basis for current research; the most fundamental of these is the problem of defining the spatial location of the entities being studied. Classification of the techniques of spatial analysis is difficult because of the large number of different fields of research involved, the different fundamental approaches which can be chosen, the many forms the data can take.
Spatial analysis can be considered to have arisen with early attempts at cartography and surveying but many fields have contributed to its rise in modern form. Biology contributed through botanical studies of global plant distributions and local plant locations, ethological studies of animal movement, landscape ecological studies of vegetation blocks, ecological studies of spatial population dynamics, the study of biogeography. Epidemiology contributed with early work on disease mapping, notably John Snow's work of mapping an outbreak of cholera, with research on mapping the spread of disease and with location studies for health care delivery. Statistics has contributed through work in spatial statistics. Economics has contributed notably through spatial econometrics. Geographic information system is a major contributor due to the importance of geographic software in the modern analytic toolbox. Remote sensing has contributed extensively in clustering analysis. Computer science has contributed extensively through the study of algorithms, notably in computational geometry.
Mathematics continues to provide the fundamental tools for analysis and to reveal the complexity of the spatial realm, for example, with recent work on fractals and scale invariance. Scientific modelling provides a useful framework for new approaches. Spatial analysis confronts many fundamental issues in the definition of its objects of study, in the construction of the analytic operations to be used, in the use of computers for analysis, in the limitations and particularities of the analyses which are known, in the presentation of analytic results. Many of these issues are active subjects of modern research. Common errors arise in spatial analysis, some due to the mathematics of space, some due to the particular ways data are presented spatially, some due to the tools which are available. Census data, because it protects individual privacy by aggregating data into local units, raises a number of statistical issues; the fractal nature of coastline makes precise measurements of its length difficult if not impossible.
A computer software fitting straight lines to the curve of a coastline, can calculate the lengths of the lines which it defines. However these straight lines may have no inherent meaning in the real world, as was shown for the coastline of Britain; these problems represent a challenge in spatial analysis because of the power of maps as media of presentation. When results are presented as maps, the presentation combines spatial data which are accurate with analytic results which may be inaccurate, leading to an impression that analytic results are more accurate than the data would indicate; the definition of the spatial presence of an entity constrains the possible analysis which can be applied to that entity and influences the final conclusions that can be reached. While this property is fundamentally true of all analysis, it is important in spatial analysis because the tools to define and study entities favor specific characterizations of the entities being studied. Statistical techniques favor the spatial definition of objects as points because there are few statistical techniques which operate directly on line, area, or volume elements.
Computer tools favor the spatial definition of objects as homogeneous and separate elements because of the limited number of database elements and computational structures available, the ease with which these primitive structures can be created. Spatial dependency is the co-variation of properties within geographic space: characteristics at proximal locations appear to be correlated, either positively or negatively. Spatial dependency leads to the spatial autocorrelation problem in statistics since, like temporal autocorrelation, this violates standard statistical techniques that assume independence among observations. For example, regression analyses that do not compensate for spatial dependency can have unstable parameter estimates and yield unreliable significance tests. Spatial regression models do not suffer from these weaknesses, it is appropriate to view spatial dependency as a source of information rather than something to be corrected. Locational effects manifest as spatial heterogeneity, or the apparent variation in a process with respect to location in geographic space.
Unless a space is uniform and boundless, every location will have some degree of uniqueness relative to the other locations. This affects the spatial dependency relations and therefore the spatial process. Spatial heterogeneity means that overall parameters estimated for the entire system may not adequately describe the