Gis Definition And Functions Pdf

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A GIS geographic or geospatial information system allows you to record a base map with a geospatial referencing system such as longitude or latitude and then to add additional layers of other information. Importantly that information is identified using the same geospatial referencing. The GIS then allows the individual layers, or themes as they are called to be linked. Analysis of the information can then be undertaken using the statistical and analytical tools that are provided as part of the GIS.

Geographic information system

A geographic information system GIS is a conceptualized framework that provides the ability to capture and analyze spatial and geographic data. GIS applications or GIS apps are computer-based tools that allow the user to create interactive queries user-created searches , store and edit spatial and non-spatial data, analyze spatial information output, and visually share the results of these operations by presenting them as maps. Geographic information science or, GIScience —the scientific study of geographic concepts, applications, and systems—is commonly initialized as GIS, as well.

Geographic information systems are utilized in multiple technologies, processes, techniques and methods. GIS provides the capability to relate previously unrelated information, through the use of location as the "key index variable". Locations and extents that are found in the Earth's spacetime , are able to be recorded through the date and time of occurrence, along with x, y, and z coordinates ; representing, longitude x , latitude y , and elevation z.

All Earth-based, spatial—temporal, location and extent references, should be relatable to one another, and ultimately, to a "real" physical location or extent. This key characteristic of GIS, has begun to open new avenues of scientific inquiry and studies. The phrase, "geographic information system", was coined by Roger Tomlinson in , when he published the scientific paper, "A Geographic Information System for Regional Planning". Ultimately, Tomlinson created a framework for a database that was capable of storing and analyzing huge amounts of data; leading to the Canadian government being able to implement its National Land-Use Management Program.

In , John Snow , an epidemiologist and physician, was able to determine the source of a cholera outbreak in London through the use of spatial analysis.

Snow achieved this through plotting the residence of each casualty on a map of the area, as well as the nearby water sources. Once these points were marked, he was able to identify the water source within the cluster that was responsible for the outbreak. This was one of the earliest successful uses of a geographic methodology in pinpointing the source of an outbreak in epidemiology.

While the basic elements of topography and theme existed previously in cartography , Snow's map was unique due to his use of cartographic methods, not only to depict, but also to analyze clusters of geographically dependent phenomena. This work was originally drawn on glass plates but later plastic film was introduced, with the advantages of being lighter, using less storage space and being less brittle, among others.

When all the layers were finished, they were combined into one image using a large process camera. Once color printing came in, the layers idea was also used for creating separate printing plates for each color.

Two additional developments are notable in the early days of GIS: Ian McHarg's publication " Design with Nature" [9] and its map overlay method and the introduction of a street network into the U. Computer hardware development spurred by nuclear weapon research led to general-purpose computer "mapping" applications by the early s.

Developed by Dr. A rating classification factor was also added to permit analysis. It supported a national coordinate system that spanned the continent, coded lines as arcs having a true embedded topology and it stored the attribute and locational information in separate files. As a result of this, Tomlinson has become known as the "father of GIS", particularly for his use of overlays in promoting the spatial analysis of convergent geographic data.

CGIS lasted into the s and built a large digital land resource database in Canada. It was developed as a mainframe -based system in support of federal and provincial resource planning and management. Its strength was continent-wide analysis of complex datasets. The CGIS was never available commercially. This was renamed in to MapInfo for Windows when it was ported to the Microsoft Windows platform. This began the process of moving GIS from the research department into the business environment.

More recently, a growing number of free, open-source GIS packages run on a range of operating systems and can be customized to perform specific tasks. Modern GIS technologies use digital information, for which various digitized data creation methods are used. The most common method of data creation is digitization , where a hard copy map or survey plan is transferred into a digital medium through the use of a CAD program, and geo-referencing capabilities. With the wide availability of ortho-rectified imagery from satellites, aircraft, Helikites and UAVs , heads-up digitizing is becoming the main avenue through which geographic data is extracted.

Heads-up digitizing involves the tracing of geographic data directly on top of the aerial imagery instead of by the traditional method of tracing the geographic form on a separate digitizing tablet heads-down digitizing. Heads-down digitizing, or manual digitizing, uses a special magnetic pen, or stylus, that feeds information into a computer to create an identical, digital map. Some tablets use a mouse-like tool, called a puck, instead of a stylus. Though heads-up digitizing is more commonly used, heads-down digitizing is still useful for digitizing maps of poor quality.

Geoprocessing is a GIS operation used to manipulate spatial data. A typical geoprocessing operation takes an input dataset , performs an operation on that dataset, and returns the result of the operation as an output dataset. Common geoprocessing operations include geographic feature overlay, feature selection and analysis, topology processing, raster processing, and data conversion. Geoprocessing allows for definition, management, and analysis of information used to form decisions.

GIS uses spatio-temporal space-time location as the key index variable for all other information. Just as a relational database containing text or numbers can relate many different tables using common key index variables, GIS can relate otherwise unrelated information by using location as the key index variable. Any variable that can be located spatially, and increasingly also temporally, can be referenced using a GIS.

Units applied to recorded temporal-spatial data can vary widely even when using exactly the same data, see map projections , but all Earth-based spatial—temporal location and extent references should, ideally, be relatable to one another and ultimately to a "real" physical location or extent in space—time.

Related by accurate spatial information, an incredible variety of real-world and projected past or future data can be analyzed, interpreted and represented. GIS accuracy depends upon source data, and how it is encoded to be data referenced. Land surveyors have been able to provide a high level of positional accuracy utilizing the GPS -derived positions.

In developing a digital topographic database for a GIS, topographical maps are the main source, and aerial photography and satellite imagery are extra sources for collecting data and identifying attributes which can be mapped in layers over a location facsimile of scale. The scale of a map and geographical rendering area representation type, or map projection , are very important aspects since the information content depends mainly on the scale set and resulting locatability of the map's representations.

A quantitative analysis of maps brings accuracy issues into focus. The electronic and other equipment used to make measurements for GIS is far more precise than the machines of conventional map analysis. GIS data represents real objects such as roads, land use, elevation, trees, waterways, etc. Real objects can be divided into two abstractions: discrete objects e.

Traditionally, there are two broad methods used to store data in a GIS for both kinds of abstractions mapping references: raster images and vector. Points, lines, and polygons represent vector data of mapped location attribute references. A new hybrid method of storing data is that of identifying point clouds, which combine three-dimensional points with RGB information at each point, returning a " 3D color image ".

GIS thematic maps then are becoming more and more realistically visually descriptive of what they set out to show or determine. There are a variety of methods used to enter data into a GIS where it is stored in a digital format. Existing data printed on paper or PET film maps can be digitized or scanned to produce digital data. A digitizer produces vector data as an operator traces points, lines, and polygon boundaries from a map. Scanning a map results in raster data that could be further processed to produce vector data.

Survey data can be directly entered into a GIS from digital data collection systems on survey instruments using a technique called coordinate geometry COGO. A current trend in data collection gives users the ability to utilize field computers with the ability to edit live data using wireless connections or disconnected editing sessions.

This eliminates the need to post process, import, and update the data in the office after fieldwork has been collected. This includes the ability to incorporate positions collected using a laser rangefinder. New technologies also allow users to create maps as well as analysis directly in the field, making projects more efficient and mapping more accurate. Remotely sensed data also plays an important role in data collection and consist of sensors attached to a platform. Sensors include cameras, digital scanners and lidar , while platforms usually consist of aircraft and satellites.

Aircraft measurement software, accurate to 0. Helikites are inexpensive and gather more accurate data than aircraft. Helikites can be used over roads, railways and towns where unmanned aerial vehicles UAVs are banned.

Recently aerial data collection has become more accessible with miniature UAVs and drones. The majority of digital data currently comes from photo interpretation of aerial photographs. Soft-copy workstations are used to digitize features directly from stereo pairs of digital photographs. These systems allow data to be captured in two and three dimensions, with elevations measured directly from a stereo pair using principles of photogrammetry.

Analog aerial photos must be scanned before being entered into a soft-copy system, for high-quality digital cameras this step is skipped. Satellite remote sensing provides another important source of spatial data.

Here satellites use different sensor packages to passively measure the reflectance from parts of the electromagnetic spectrum or radio waves that were sent out from an active sensor such as radar. Remote sensing collects raster data that can be further processed using different bands to identify objects and classes of interest, such as land cover.

Web mining is a novel method of collecting spatial data. Researchers build a web crawler application to aggregate required spatial data from the web. When data is captured, the user should consider if the data should be captured with either a relative accuracy or absolute accuracy, since this could not only influence how information will be interpreted but also the cost of data capture. After entering data into a GIS, the data usually requires editing, to remove errors, or further processing.

For vector data it must be made "topologically correct" before it can be used for some advanced analysis. For example, in a road network, lines must connect with nodes at an intersection. Errors such as undershoots and overshoots must also be removed.

For scanned maps, blemishes on the source map may need to be removed from the resulting raster. For example, a fleck of dirt might connect two lines that should not be connected. Data restructuring can be performed by a GIS to convert data into different formats. For example, a GIS may be used to convert a satellite image map to a vector structure by generating lines around all cells with the same classification, while determining the cell spatial relationships, such as adjacency or inclusion.

Since digital data is collected and stored in various ways, the two data sources may not be entirely compatible. So a GIS must be able to convert geographic data from one structure to another.

In so doing, the implicit assumptions behind different ontologies and classifications require analysis. The earth can be represented by various models, each of which may provide a different set of coordinates e. The simplest model is to assume the earth is a perfect sphere. As more measurements of the earth have accumulated, the models of the earth have become more sophisticated and more accurate.

In fact, there are models called datums that apply to different areas of the earth to provide increased accuracy, like North American Datum of for U.

What is GIS?

A geographic information system GIS is a conceptualized framework that provides the ability to capture and analyze spatial and geographic data. GIS applications or GIS apps are computer-based tools that allow the user to create interactive queries user-created searches , store and edit spatial and non-spatial data, analyze spatial information output, and visually share the results of these operations by presenting them as maps. Geographic information science or, GIScience —the scientific study of geographic concepts, applications, and systems—is commonly initialized as GIS, as well. Geographic information systems are utilized in multiple technologies, processes, techniques and methods. GIS provides the capability to relate previously unrelated information, through the use of location as the "key index variable". Locations and extents that are found in the Earth's spacetime , are able to be recorded through the date and time of occurrence, along with x, y, and z coordinates ; representing, longitude x , latitude y , and elevation z.

A geographic information system GIS is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data. The key word to this technology is Geography — this means that some portion of the data is spatial. In other words, data that is in some way referenced to locations on the earth. Coupled with this data is usually tabular data known as attribute data. Attribute data can be generally defined as additional information about each of the spatial features. An example of this would be schools. The actual location of the schools is the spatial data.

This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Leveled by. By relating seemingly unrelated data, GIS can help individuals and organizations better understand spatial patterns and relationships. GIS can use any information that includes location. The location can be expressed in many different ways, such as latitude and longitude , address, or ZIP code. Many different types of information can be compared and contrasted using GIS. The system can include data about people, such as population , income , or education level.

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What is GIS? A framework to organize, communicate, and understand the science of our world. A geographic information system GIS is a framework for gathering, managing, and analyzing data. Rooted in the science of geography, GIS integrates many types of data. It analyzes spatial location and organizes layers of information into visualizations using maps and 3D scenes.

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This chapter introduces the most powerful analytical toolset that we have in GIS. Map algebra is inherently raster-based and therefore not often taught in introductory GIS courses, except for applications in resource management. Traditional vector-based GIS basically knows the buffer and overlay Show page numbers Download PDF. Search form icon-arrow-top icon-arrow-top.

А как же проваливай и умри. ГЛАВА 36 Ручное отключение. Сьюзан отказывалась что-либо понимать. Она была абсолютно уверена, что не вводила такой команды - во всяком случае, намеренно. Подумала, что, может быть, спутала последовательность нажатия клавиш.

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2 Response
  1. Valentine R.

    Geographic Information System GIS is a computer system build to capture, store, manipulate, analyze, manage and display all kinds of spatial or geographical data.

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