Computer representations of geographic information 82 .. and an index. The book is also made available as an electronic PDF document which can. Introduction. Geographical Information System (GIS) is a technology that provides the means to collect and use geographic data to assist in the development of. Geographic information systems (GIS) apply computer technology to the tasks of This view of a GIS as an automated mapping system is much too simplistic.
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Geographic Information Systems was developed at Central Oregon . Geographic Information Systems combine spatial data (maps) with tabular data. Like the field of geography, the term Geographic Information System (GIS) is hard to Geographic information systems have emerged in the last decade as an. This is the book Geographic Information System Basics (v. ). This book is licensed under a . Geographic Information Systems for Today and Beyond.
A two-dimensional contour map created from the surface modeling of rainfall point measurements may be overlaid and analyzed with any other map in a GIS covering the same area. This GIS derived map can then provide additional information - such as the viability of water power potential as a renewable energy source. Similarly, GIS can be used to compare other renewable energy resources to find the best geographic potential for a region.
Additionally, from a series of three-dimensional points, or digital elevation model , isopleth lines representing elevation contours can be generated, along with slope analysis, shaded relief , and other elevation products. Watersheds can be easily defined for any given reach, by computing all of the areas contiguous and uphill from any given point of interest.
Similarly, an expected thalweg of where surface water would want to travel in intermittent and permanent streams can be computed from elevation data in the GIS.
A GIS can recognize and analyze the spatial relationships that exist within digitally stored spatial data. These topological relationships allow complex spatial modelling and analysis to be performed. Topological relationships between geometric entities traditionally include adjacency what adjoins what , containment what encloses what , and proximity how close something is to something else.
Geometric networks are linear networks of objects that can be used to represent interconnected features, and to perform special spatial analysis on them. A geometric network is composed of edges, which are connected at junction points, similar to graphs in mathematics and computer science. Just like graphs, networks can have weight and flow assigned to its edges, which can be used to represent various interconnected features more accurately.
Geometric networks are often used to model road networks and public utility networks, such as electric, gas, and water networks. Network modeling is also commonly employed in transportation planning , hydrology modeling, and infrastructure modeling.
GIS hydrological models can provide a spatial element that other hydrological models lack, with the analysis of variables such as slope, aspect and watershed or catchment area. Slope and aspect can then be used to determine direction of surface runoff, and hence flow accumulation for the formation of streams, rivers and lakes.
Areas of divergent flow can also give a clear indication of the boundaries of a catchment. Once a flow direction and accumulation matrix has been created, queries can be performed that show contributing or dispersal areas at a certain point. One of the main uses of hydrological modeling is in environmental contamination research. Other applications of hydrological modeling include groundwater and surface water mapping , as well as flood risk maps.
Dana Tomlin probably coined the term "cartographic modeling" in his PhD dissertation ; he later used it in the title of his book, Geographic Information Systems and Cartographic Modeling Tomlin used raster layers, but the overlay method see below can be used more generally.
Operations on map layers can be combined into algorithms, and eventually into simulation or optimization models.
The combination of several spatial datasets points, lines, or polygons creates a new output vector dataset, visually similar to stacking several maps of the same region.
These overlays are similar to mathematical Venn diagram overlays. A union overlay combines the geographic features and attribute tables of both inputs into a single new output. An intersect overlay defines the area where both inputs overlap and retains a set of attribute fields for each. A symmetric difference overlay defines an output area that includes the total area of both inputs except for the overlapping area. Data extraction is a GIS process similar to vector overlay, though it can be used in either vector or raster data analysis.
Rather than combining the properties and features of both datasets, data extraction involves using a "clip" or "mask" to extract the features of one data set that fall within the spatial extent of another dataset.
In raster data analysis, the overlay of datasets is accomplished through a process known as "local operation on multiple rasters" or " map algebra ", through a function that combines the values of each raster's matrix. This function may weigh some inputs more than others through use of an "index model" that reflects the influence of various factors upon a geographic phenomenon.
Geostatistics is a branch of statistics that deals with field data, spatial data with a continuous index. It provides methods to model spatial correlation, and predict values at arbitrary locations interpolation. When phenomena are measured, the observation methods dictate the accuracy of any subsequent analysis. Due to the nature of the data e. This loss of precision is determined from the scale and distribution of the data collection. To determine the statistical relevance of the analysis, an average is determined so that points gradients outside of any immediate measurement can be included to determine their predicted behavior.
This is due to the limitations of the applied statistic and data collection methods, and interpolation is required to predict the behavior of particles, points, and locations that are not directly measurable.
Interpolation is the process by which a surface is created, usually a raster dataset, through the input of data collected at a number of sample points.
There are several forms of interpolation, each which treats the data differently, depending on the properties of the data set. In comparing interpolation methods, the first consideration should be whether or not the source data will change exact or approximate. Next is whether the method is subjective, a human interpretation, or objective.
Then there is the nature of transitions between points: Finally, there is whether a method is global it uses the entire data set to form the model , or local where an algorithm is repeated for a small section of terrain. Interpolation is a justified measurement because of a spatial autocorrelation principle that recognizes that data collected at any position will have a great similarity to, or influence of those locations within its immediate vicinity.
Digital elevation models , triangulated irregular networks , edge-finding algorithms, Thiessen polygons , Fourier analysis , weighted moving averages , inverse distance weighting , kriging , spline , and trend surface analysis are all mathematical methods to produce interpolative data. A reference theme is required to geocode individual addresses, such as a road centerline file with address ranges.
The individual address locations have historically been interpolated, or estimated, by examining address ranges along a road segment. These are usually provided in the form of a table or database. The software will then place a dot approximately where that address belongs along the segment of centerline. Geocoding can also be applied against actual parcel data, typically from municipal tax maps. In this case, the result of the geocoding will be an actually positioned space as opposed to an interpolated point.
This approach is being increasingly used to provide more precise location information. Reverse geocoding is the process of returning an estimated street address number as it relates to a given coordinate. For example, a user can click on a road centerline theme thus providing a coordinate and have information returned that reflects the estimated house number. This house number is interpolated from a range assigned to that road segment. Note that reverse geocoding does not return actual addresses, only estimates of what should be there based on the predetermined range.
Coupled with GIS, multi-criteria decision analysis methods support decision-makers in analysing a set of alternative spatial solutions, such as the most likely ecological habitat for restoration, against multiple criteria, such as vegetation cover or roads. MCDA uses decision rules to aggregate the criteria, which allows the alternative solutions to be ranked or prioritised. Cartography is the design and production of maps, or visual representations of spatial data.
The vast majority of modern cartography is done with the help of computers, usually using GIS but production of quality cartography is also achieved by importing layers into a design program to refine it. First, it produces graphics on the screen or on paper that convey the results of analysis to the people who make decisions about resources. Wall maps and other graphics can be generated, allowing the viewer to visualize and thereby understand the results of analyses or simulations of potential events.
Web Map Servers facilitate distribution of generated maps through web browsers using various implementations of web-based application programming interfaces AJAX , Java , Flash , etc. Second, other database information can be generated for further analysis or use. Traditional maps are abstractions of the real world, a sampling of important elements portrayed on a sheet of paper with symbols to represent physical objects. People who use maps must interpret these symbols. Topographic maps show the shape of land surface with contour lines or with shaded relief.
Today, graphic display techniques such as shading based on altitude in a GIS can make relationships among map elements visible, heightening one's ability to extract and analyze information.
A GIS was used to register and combine the two images to render the three-dimensional perspective view looking down the San Andreas Fault , using the Thematic Mapper image pixels, but shaded using the elevation of the landforms.
An archeochrome is a new way of displaying spatial data. It is suited to the visual display of heat-loss data. These tools can come in the form of add-ins to existing wider-purpose software such as spreadsheets. GIS or spatial data mining is the application of data mining methods to spatial data.
Typical applications include environmental monitoring. A characteristic of such applications is that spatial correlation between data measurements require the use of specialized algorithms for more efficient data analysis. The implementation of a GIS is often driven by jurisdictional such as a city , purpose, or application requirements.
Generally, a GIS implementation may be custom-designed for an organization. Hence, a GIS deployment developed for an application, jurisdiction, enterprise, or purpose may not be necessarily interoperable or compatible with a GIS that has been developed for some other application, jurisdiction, enterprise, or purpose. GIS provides, for every kind of location-based organization, a platform to update geographical data without wasting time to visit the field and update a database manually.
GIS when integrated with other powerful enterprise solutions like SAP  and the Wolfram Language  helps creating powerful decision support system at enterprise level. Compliance tests are not available for all specifications. These services give the public access to huge amounts of geographic data; perceived by many users to be as trustworthy and usable as professional information.
Some of them, like Google Maps and OpenLayers , expose an application programming interface API that enable users to create custom applications. Web mapping has also uncovered the potential of crowdsourcing geodata in projects like OpenStreetMap , which is a collaborative project to create a free editable map of the world. These mashup projects have been proven to provide a high level of value and benefit to end users outside that possible through traditional geographic information.
The condition of the Earth's surface, atmosphere, and subsurface can be examined by feeding satellite data into a GIS. As an example, the changes in vegetation vigor through a growing season can be animated to determine when drought was most extensive in a particular region.
The resulting graphic represents a rough measure of plant health. Working with two variables over time would then allow researchers to detect regional differences in the lag between a decline in rainfall and its effect on vegetation.
The satellite sensor output used to generate a vegetation graphic is produced for example by the advanced very-high-resolution radiometer AVHRR. This sensor system detects the amounts of energy reflected from the Earth's surface across various bands of the spectrum for surface areas of about 1 square kilometer.
The satellite sensor produces images of a particular location on the Earth twice a day. In addition to the integration of time in environmental studies, GIS is also being explored for its ability to track and model the progress of humans throughout their daily routines. A concrete example of progress in this area is the recent release of time-specific population data by the U. In this data set, the populations of cities are shown for daytime and evening hours highlighting the pattern of concentration and dispersion generated by North American commuting patterns.
Tools and technologies emerging from the World Wide Web Consortium 's Semantic Web are proving useful for data integration problems in information systems. Ontologies are a key component of this semantic approach as they allow a formal, machine-readable specification of the concepts and relationships in a given domain.
This in turn allows a GIS to focus on the intended meaning of data rather than its syntax or structure. For example, reasoning that a land cover type classified as deciduous needleleaf trees in one dataset is a specialization or subset of land cover type forest in another more roughly classified dataset can help a GIS automatically merge the two datasets under the more general land cover classification.
Also, simpler ontologies and semantic metadata standards are being proposed by the W3C Geo Incubator Group  to represent geospatial data on the web.
With the popularization of GIS in decision making, scholars have begun to scrutinize the social and political implications of GIS. At the end of the 20th century, GIS began to be recognized as tools that could be used in the classroom. GIS seem to provide many advantages in teaching geography because they allow for analyses based on real geographic data and also help raise many research questions from teachers and students in classrooms, as well as they contribute to improvement in learning by developing spatial and geographical thinking and, in many cases, student motivation.
GIS is proven as an organization-wide, enterprise and enduring technology that continues to change how local government operates. From Wikipedia, the free encyclopedia. For other uses, see GIS disambiguation. System to capture, manage and present geographic data. Main article: GIS file formats. Map projection. Further information: Spatial analysis. Open Geospatial Consortium. Web mapping. See also: Historical geographic information system and Time geography. Main articles: Neogeography and Public participation GIS.
Esri Education User Conference. Atlas portal. Advances in geographic information systems, computers, environment and urban systems, Vol. Old principles with new capabilities". Urban Design International. GIScience in ". Journal of Spatial Information Science 1. Retrieved 18 April Archived from the original on 17 December Retrieved 16 December Retrieved 10 May Design with nature.
Natural History Press. January Cartography and Geographic Information Systems. Archived from the original on 4 June Retrieved 9 June Archived from the original on 14 July Harvard University. Archived from the original on 13 December Retrieved 21 March Web GIS: Principles and Applications.
ESRI Press. Redlands, CA. Perspectives from the Pioneers. Retrieved 5 May What Are the Differences? Photogrammetric engineering and remote sensing. Archived from the original PDF on 24 April Retrieved 17 September National Standard for Spatial Data Accuracy". Archived from the original on 6 November Retrieved 13 May Journal of Archaeological Science: Kendig ed.
Natural Kinds and Classification in Scientific Practice. Introduction to Geographical Information Systems. New York: McGraw Hill. Geographic Information Systems and Science. West Sussex, England: John Wiley and Sons: International Journal of Geographical Information Science. Computers and Geosciences. Geographical Analysis.
Calvert, J. Pearce, W. For example, spot elevation measure- hosting the database and serving data over the ments would be represented by points, contours local network and internet. A large percentage be represented by a raster, or digital image, of research and organizational data that is col- where each pixel represents the elevation value lected has a spatial component and is thus suit- at that location.
This means that this In addition to its type of geometry, a feature data can be referenced to a location and visu- class can be defined by the attributes associated alized in the form of a map or globe and then with it.
For example, the location of a particu- analyzed to reveal relationships, patterns, and lar plant that is represented as a point might trends. This combination of a map with ing layers in GIS software. This quickly allows a database allows for easy visualization of the spatial relationships between the layers to be data in GIS software, where the points repre- discovered, such as the correlations between senting plants can be labeled with their names, precipitation, elevation, and vegetation types.
A data model can be thought of as a database design or template that care- fully considers how real-world features are represented as geometry in feature classes, the attributes appropriate for each feature, and any known rela- tionships that exist between individual features or entire feature classes.
These models can be Open Source vs. Commercial downloaded for free and allow scientists to get started with their GIS projects quickly, with- Software out the need to design their own models. Data There is much debate within the GIS devel- models like the one developed by the Alliance oper and user community regarding the for Public Gardens GIS ArcGIS Public Garden choice of commercial software versus open Data Model additionally provide standardiza- tion across multiple organizations, thus simpli- source software.
Commercial products like fying the exchange of critical biodiversity data. A common starting point is to collect as much existing data faces and sophisticated analysis tools. Con- as is readily available through internet data versely, open source solutions such as those repositories like the U. One of the primary sources of this data is from a technique called remote sens- more difficult to operate and get support for.
See next article for source software for GIS applications and more on the use of remote sensing. Remotely sensed imagery frequently trees in decline, then buffering, flow analysis, serves as a base map or background that other and spatial statistics can be used to attempt to data—location of roads, vegetation types, etc.
Many of these analysis capabilities are built When this data is not sufficient for identify- into most desktop GIS software packages in the ing features such as the location and species of form of geoprocessing tools.
These tools can be plants, it is customary to collect additional data used individually or grouped together into an in the field by using GPS or traditional survey- analysis workflow called a model. This kind of ing techniques. Once the necessary geographic and attribute Once the phase of spatial analysis is com- data are collected for a project, the next step is pleted and a relationship, pattern, or trend has to harness the true power of GIS to analyze this been revealed or confirmed, the final step is information in an effort to understand, ques- to summarize the results of the analysis as an tion, interpret, and visualize it to reveal rela- information product that can be used to make tionships, patterns, and trends.
One common decisions and take informed action. Most desk- type of analysis is to investigate quantities. Most desktop GIS soft- a combination thereof. The plant scientists ware packages provide a suite of tools for work- investigating the previously mentioned cluster ing with this type of information in the form of of declining trees may have determined that densities, clusters, and distributions.
Another increased earthquake activity on a nearby fault common analysis is to look at what is nearby. Louis, Missouri. Since the study of land and the Our ever increasing need for land and resources process of delineating boundaries are inherently combined with the threat of climate change has spatial in nature, GIS is cited as the overwhelm- pushed the assessment of biodiversity to the top ing choice of tool for the task. In addition to of the list of plant science research priorities.
GIS is often cited soil, geology, and land use data. In a forest con- as the primary tool used to perform many of servation study in Malaysia the investigators these studies, which frequently employ species used a decision making approach that assigns occurrence data from informatics sites like the weighted values to possible alternatives in an Global Biodiversity Information Facility GBIF effort to prioritize areas for conservation.
This and remotely sensed data from satellites like study considered species and ecosystem diver- Landsat 7 TM to determine the relative species sity, the soil and water conservation functions richness of a particular area. In one study of of plants, and potential threats to the forest, and African vascular plant diversity, the investiga- through a process called map algebra, hot spots tors performed a multivariate analysis to deter- for conservation were determined and used to mine the relationship between the number of delineate potential new protection areas Phua species in well-known areas and the associated and Minowa Traditional This relationship was then used to interpolate approaches to expedition planning have favored the species richness in lesser-known areas to areas that were considered interesting or easily produce a vascular plant diversity map for the accessible, and tended to focus on species that entire continent Mutke et al.
Here spot elevations are shown as points, contours are shown as lines, ponds are shown as polygons, and an elevation surface is shown as a raster in part of the Arnold Arboretum. GIS lizes existing biodiversity data along with is commonly used for creating collection maps topography, geology, vegetation, temperature, and planting plans, identifying problems and and precipitation data to determine areas that threats, planning mitigation, and performing have the greatest potential to provide the maxi- research.
In addition to data about the living mum amount of new information and speci- collection, a typical garden GIS employs data on mens. In a survey gap analysis study in Guyana topography, soils, hydrology, land use, facilities, the investigators used museum and herbaria transportation and more. In a tree conserva- specimen data to locate geographical gaps in the tion study at the University of California—Davis existing data in an effort to determine candidate Arboretum the investigators used data on the survey sites for each taxonomic group of inter- location, species, size, and condition of each est.
These candidate sites were then compared specimen in conjunction with data on site char- with weighted abiotic variables to determine a acteristics and conflicting urban infrastructure final set of collecting sites that had the great- to determine a condition rating and a hazard est chance of producing new information and rating for each tree in the collection. These rat- specimens for each taxonomic group Funk et ings were then used to identify areas of concern al.