<h5 id="what-is-spatial-lnformation-technoloos">What is Spatial lnformation Technoloos?</h5> <ul> <li>Spatial Information Technology is a field related to the use of technology in managing data with spatial components.</li> <li>It involves collecting, storing, retrieving, displaying, manipulating, managing, and analyzing spatial information.</li> <li>Spatial information often has physically measurable dimensions and can include data such as addresses or boundaries.</li> <li>This technology is a combination of Remote Sensing, GPS, GIS, Digital Cartography, and Database Management Systems.</li> <li>It is used in various fields such as agriculture, urban planning, environmental studies, and transportation.</li> </ul> <p>======</p> <h5 id="what-is-gis-geographical-information-system">What is GIS (Geographical Information System)?</h5> <ul> <li>GIS, or Geographical Information System, is a computing system that processes georeferenced information.</li> <li>It was enabled by advance computing systems since the mid 1970’s for organizing spatial and attribute data.</li> <li>GIS is defined as a system for capturing, storing, checking, integrating, manipulating, analyzing and displaying spatially referenced data.</li> <li>It is a combination of Computer Assisted Cartography and Database Management System.</li> <li>GIS draws methodological strength from various spatial and allied sciences such as Computer Science, Statistics, Cartography, Remote Sensing, Database Technology, Geography, Geology, Hydrology, Agriculture, Resource Management, Environmental Science, and Public Administration.</li> </ul> <p>======</p> <h5 id="forms-of-geographical-information">Forms of Geographical Information</h5> <ul> <li>Geographical information is represented by two types of data: spatial and non-spatial.</li> <li>Spatial data can take the form of points, lines, or areas and must be registered to a coordinate system for storage in a GIS.</li> <li>Non-spatial or attribute data describe spatial data and can include information such as cycle parts or state names with definite locations.</li> <li>Spatial data can be acquired digitally, digitized from analogue sources, or collected through original surveys.</li> <li>The choice of a spatial data source is determined by the application area, budget, and data structure (vector/raster).</li> <li>Common sources of spatial data include topographical or thematic maps in hard copy or digital formats, characterized by scale, symbols, and a coordinate system.</li> </ul> <p>======</p> <h5 id="adrantages-of-gis-orer-manual-methods">Adrantages of GIS orer Manual Methods</h5> <ul> <li>Maps have limitations such as processing and presenting information in a particular way, showing predetermined themes, and requiring a new map for information alteration.</li> <li>A GIS has separate data storage and presentation, providing options for viewing and presenting data in various ways.</li> <li>Users can retrieve associated attribute information for analysis and draw maps by querying or analyzing attribute data.</li> <li>Spatial operations like polygon overlay or buffering can be applied to generate new sets of information.</li> <li>Different items of attribute data can be associated with one another through shared location coding.</li> </ul> <p>======</p> <h5 id="components-of-gis">Components of GIS</h5> <ul> <li>A Geographical Information System (GIS) consists of five essential components.</li> <li>(a) Hardware: The physical devices and infrastructure required to run a GIS, such as computers, servers, and storage devices.</li> <li>(b) Software: The programs and systems used to manage, analyze, and visualize spatial data, such as GIS applications and databases.</li> <li>(c) Data: The geographical and spatial information used in a GIS, which can include maps, images, and other datasets.</li> <li>(d) People: The users, managers, and administrators who operate and maintain a GIS.</li> <li>(e) Procedures: The methods and processes used to manage and use a GIS, including data collection, analysis, and visualization.</li> </ul> <p>======</p> <h5 id="hardware">Hardware</h5> <ul> <li>The GIS has three major components: hardware, software, and database management system.</li> <li>The hardware component includes processing, storage, display, and input and output sub-systems.</li> <li>The software component includes modules for data entry, editing, maintenance, analysis, transformation, manipulation, data display, and output.</li> <li>The database management system is responsible for data organization.</li> <li>No equations or formulae are provided in the text.</li> <li>Examples and their solutions are also not included in the text.</li> </ul> <p>======</p> <h5 id="software">Software</h5> <ul> <li>A GIS requires an application software with functional modules related to data entry, editing, and maintenance.</li> <li>Analysis, transformation, and manipulation of data are also crucial functional modules in a GIS.</li> <li>Data display is an essential software component of a GIS.</li> <li>Output generation is another critical software module in a GIS.</li> <li>The software modules work together to fulfill the prerequisites of a GIS.</li> </ul> <p>======</p> <h5 id="data">Data</h5> <ul> <li>Spatial data and related tabular data form the core of Geographic Information Systems (GIS).</li> <li>Digital maps serve as the fundamental input for GIS, representing the basic spatial data.</li> <li>Tabular data associated with map objects can be linked to the digital data, enhancing the information content.</li> <li>GIS has the capability to integrate spatial data with other data resources, promoting comprehensive data analysis.</li> <li>For advanced data management, GIS can utilize a Database Management System (DBMS).</li> </ul> <p>======</p> <h5 id="people">People</h5> <ul> <li>GIS users encompass a diverse group of individuals, including hardware and software engineers, resources and environmental scientists, as well as policy-makers and implementing agencies.</li> <li>The application of GIS is directed towards the development of a decision support system.</li> <li>GIS is employed by these users to solve real-time problems.</li> <li>The use of GIS transcends various fields, including resources, environment, and policy-making.</li> <li>GIS is a valuable tool for monitoring and implementing agencies.</li> </ul> <p>======</p> <h5 id="procedures">Procedures</h5> <ul> <li>A procedure is a series of steps followed to achieve a specific outcome.</li> <li>In the context of data management, procedures involve retrieving, inputting, storing, managing, transforming, analyzing, and presenting data.</li> <li>The basic components of a Geographic Information System (GIS) include hardware, software, data, people, and methods (Fig. 4.2).</li> <li>Retrieved data can be input into the system through various methods, such as digitizing, scanning, or direct data entry.</li> <li>Stored data is managed through database management systems, which allow for efficient data organization and retrieval.</li> <li>Transformed data undergoes processes such as cleaning, validation, and analysis before being presented in a final output.</li> </ul> <p>======</p> <h5 id="spatial-data-formats">Spatial Data Formats</h5> <ul> <li>Spatial data can be represented in two primary formats: raster and vector.</li> <li>Raster data formats divide the area into grids, with each cell containing a value. This format is ideal for representing continuous phenomena like temperature or elevation.</li> <li>Vector data formats, on the other hand, use points, lines, and polygons to represent spatial features. This format is suitable for discrete features like buildings or roads.</li> <li>Within vector data formats, there are further distinctions between point, line, and polygon data types.</li> <li>Raster and vector data formats each have their strengths and weaknesses, and the choice between them depends on the specific use case and the nature of the spatial data being represented.</li> </ul> <p>======</p> <h5 id="raster-data-format">Raster Data Format</h5> <ul> <li>Raster data represent graphic features as a pattern of grids of squares, with each square (cell) assigned a value based on the attribute at that position.</li> <li>The relationship between cell size and the number of cells is expressed as the resolution of the raster. The grid size affects the level of detail in the raster data.</li> <li>Raster files are often used for digital representations of aerial photographs, satellite images, scanned paper maps, etc.</li> <li>They are most suitable when cost needs to be kept down, map does not require analysis of individual map features, and when “backdrop” maps are required.</li> <li>An example of raster data is a scanned image of a topographic map.</li> </ul> <p>======</p> <h5 id="vector-data-format">Vector Data Format</h5> <ul> <li> <p>Vector data representation records the position of features using coordinates, with each point being expressed as two or three numbers (X, Y or X, Y, Z coordinates).</p> </li> <li> <p>A vector data model uses points stored by their real (earth) coordinates, with lines and areas being built from sequences of points. It can store information about topology and is best input through manual digitizing.</p> </li> <li> <p>Vector files are commonly used for highly precise applications, when file sizes are important, when individual map features require analysis, and when descriptive information must be stored.</p> </li> <li> <p>The advantages of vector data formats include:</p> <ul> <li>Superior for storing discrete objects</li> <li>Scalable</li> <li>Less storage required for detailed data</li> </ul> </li> <li> <p>The disadvantages of vector data formats include:</p> <ul> <li>More complex and time-consuming to process</li> <li>Difficult to display smoothly (without gaps) when zooming out.</li> </ul> </li> </ul> <p>======</p> <h5 id="sequence-of-gis-activities">Sequence of GIS Activities</h5> <ul> <li>The first activity in GIS-related work is spatial data input, which involves capturing or collecting geographical data.</li> <li>The second activity is entering attribute data, which includes additional information about the features in the spatial data.</li> <li>Data verification and editing is the third activity, ensuring the accuracy and quality of the data.</li> <li>Spatial and attribute data linkages is the fourth activity, which involves connecting the spatial and attribute data.</li> <li>The final activity is spatial analysis, which uses the linked data to analyze and interpret geographical phenomena.</li> </ul> <p>======</p> <h5 id="spatial-data-input">Spatial Data Input</h5> <ul> <li>Spatial data can be acquired from digital data sets or created by manual input.</li> <li>Digital data sets can be obtained from data suppliers in various formats such as DAT tapes, CD ROMS, and floppy disks. Compatibility of data from different sources is crucial and depends on factors like projection, scale, base level, description in attributes, data collection techniques, sampling strategy, data quality, classification, interpolation methods, size and shape of mapping units, and length of the record.</li> <li>Manual data input involves entering spatial data, attribute data, verifying and editing, and linking spatial and attribute data. This process depends on the database structure, which can be vector or raster.</li> <li>Vector data is typically input using digitization or scanning, where points, lines, and/or polygons are defined using a series of coordinates.</li> <li>Scanning is a common method for inputting spatial data into a GIS, where geographical data is obtained by referring to the geographical referencing systems of the map or aerial photograph, or by overlaying a graticule or grid onto it.</li> </ul> <p>======</p> <h5 id="scanners">Scanners</h5> <ul> <li>Scanners are devices that convert analogue data into digital grid-based images.</li> <li>There are two basic types: step-for-step scanners and whole document scanners. Step-for-step scanners use a movable arm with a source of illumination (like LEDs or a stabilized fluorescent lamp) and a digital camera with high-resolution CCD sensors.</li> <li>Whole document scanners can scan an entire document in one operation. They are often mounted on a stand with a fixed illumination source and camera array, while the document is moved past by a feeding mechanism.</li> <li>The resolution of modern document scanners is determined by the geometry of the sensor surface and the amount of memory, not a mechanical arm.</li> <li>The scanned image is never perfect and usually contains all the defects of the original map. Excess data must be removed to make the digital image usable.</li> </ul> <p>======</p> <h5 id="entering-the-attribute-data">Entering the Attribute Data</h5> <ul> <li>Attribute data in GIS refers to properties of spatial entities that are not spatial.</li> <li>These data can define features like color, symbol, or data location of a road.</li> <li>Additional attribute values, such as road width or surface type, can be stored as spatial or non-spatial information.</li> <li>Attribute data can be sourced from various places like published records, censuses, surveys, or spreadsheets.</li> <li>The data can be manually entered or imported into a GIS database using a standard transfer format.</li> </ul> <p>======</p> <h5 id="data-verification-and-editing">Data Verification and Editing</h5> <ul> <li>Verification of spatial data in GIS is essential to identify and correct errors, which can be caused during digitization such as data omissions, under/overshoots.</li> <li>Errors in spatial data can be categorized into:</li> </ul> <p>======</p> <h5 id="geographic-data--linkages-and-matching">Geographic Data : Linkages and Matching</h5> <ul> <li>Linkages in GIS: GIS combines different data sets, such as linking the number of children under 10 years of age with the mortality rate from malnutrition to obtain the desired answer.</li> <li>Exact Matching: It involves bringing together information from two files about the same set of geographic features using a key common to both files, such as the name of the towns.</li> <li>Hierarchical Matching: It is used when information is collected in more detail and less frequently than other types of information. The smaller areas are grouped to match the bigger ones exactly, such as land use and land transformation data.</li> <li>Fuzzy Matching: This method is used when the boundaries of the smaller areas do not match with those of the larger ones, such as crop boundaries and soil types. A GIS can overlay the two sets and compute crop productivity for each soil type.</li> <li>Spatial information in GIS is linked only when they relate to the same geographical area.</li> </ul> <p>======</p> <h5 id="spatial-analysis">Spatial Analysis</h5> <ul> <li>GIS has strong analytical capabilities, with spatial analysis functions that use spatial and non-spatial attributes in the database to answer questions about the real world.</li> <li>Overlay analysis is a key GIS function, allowing for the integration of multiple layers of maps using overlay operations to obtain a new map layer.</li> <li>Overlay analysis can be used to study changes in land use/land cover over two different periods in time and analyze land transformations.</li> <li>Buffer operation is another important spatial analysis function in GIS, used to create a buffer of a certain specified distance along any point, line or area feature.</li> <li>Buffer operation can be used for proximity analysis, such as locating areas/population benefitted or denied of facilities and services, and studying the impact of point sources of air, noise or water pollution on human health.</li> </ul> <p>======</p>