Introduction to GIS

A Geographic Information System (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.

1. GEOGRAPHIC INFORMATION SYSTEM (GIS) Mashhood Arif

2. Contents What is GIS? Components of GIS GIS Process Functions of GIS Applications of GIS Data Structure Data File Formats Map & Map Elements Data Modelling GIS Data Sources Geospatial Analysis Conclusion

3. What is GIS? “A system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data which are spatially referenced to the Earth. This is normally considered to involve a spatially referenced computer database and appropriate applications software” A set of tools for Collecting Storing Manipulating Retrieving Transforming and Display of Spatial Data from the Real World

4. GEOGRAPHIC implies that locations of the data items are known, or can be calculated, in terms of Geographic coordinates (Latitude, Longitude) INFORMATION implies that the data in a GIS are organized to yield useful knowledge, often as colored maps and images, but also as statistical graphics, tables, and various on-screen responses to interactive queries SYSTEM implies that a GIS is made up from several inter-related and linked components with different functions. Thus, GIS have functional capabilities for data capture, input, manipulation, transformation, visualization, combinations, query, analysis, modelling and output

5. Components of GIS GIS links locational (spatial) and database (tabular) information and enables a person to visualize patterns, relationships and trends. The five components of GIS are as under: Hardware Software Data People Methods

6. Hardware Systems to support rapid graphic analysis and processing (CPU, processor, keyboard etc.) Software A technology for storing and analyzing location and attribute data (ArcGIS, Map Info, AutoDesk Map etc.) Data Geographical data in form of hardcopy map, digital map, aerial photos, satellite images, other documents for GIS operations Methods Various procedures including analysis, manipulation, presentation, visualization, modelling People Different user and GIS application experts

7. GIS Process Links databases and maps Manages information about places Helps answer questions such as: Where is it? What else is nearby? Where is the highest concentration of ‘X’? Where can I find things with characteristic ‘Y’? Where is the closest ‘Z’ to my location?

8. Functions of GIS Data Capture Data Storage & Management Data Display Data Editing, Manipulation and Analysis Presentations & Visualization

9. Applications of GIS Agriculture Archaeology Architecture/Landscape Arch. Business Computer Science Environmental Science Engineering Journalism Military Science Natural Resource Management Geography Geology Meteorology Oceanography Law Enforcement Public Health History Sociology Urban/Regional Planning

10. Data Structure

11. GIS Data Formats (file formats) Shapefiles Coverages TIN (e.g. elevation can be stored as TIN) Triangulated Irregular Network Grid (e.g. elevation can be stored as Grid) Image (e.g. elevation can be stored as image, all remote sensing images ) Vector data Raster data

12. Shape Files Nontopological Advantages no overhead to process topology Disadvantages polygons are double digitized, no topologic data checking At least 3 files . shp . shx .dbf

13. Coverages Original ArcInfo Format Directory With Several Files Database Files are stored in the Info Directory Uses Arc Node Topology Containment (coincident) Connectivity Adjacency

14. TIN A triangulated irregular network (TIN) is a data model that is used to represent three dimensional objects. In this case, x,y , and z values represent points. Using methods of computational geometry, the points are connected into what is called a triangulation, forming a network of triangles. The lines of the triangles are called edges , and the interior area is called a face, or facet . The illustration shows how we can create a TIN of the terrain First, a series of elevation points are created Second, a TIN face is created with the elevation data Third, the faces are shaded in to give the impression of a 3D surface

15. Components of a TIN Nodes Edges Triangles Hull Topology ©Arthur J. Lembo Cornell University

16. Map & Map Elements Maps provide two types of information: Locational I nformation and Spatial Relationships Maps contain POINT features, LINE features and AREA features Point Features Line Features Area Features Spatially distributed entities, activities or events Points have a single geographic coordinate such as: Tree, t raffic accident, lamp post Spatially distributed entities, activities or events Lines (Arcs) are a series of geographic coordinates joined to form a line such as: Road, s tream, r ailway Spatially distributed entities, activities or o events Areas (Polygons) are a series of geographic coordinates joined together to form a boundary such as: Lake, soil types

17. Data Modelling Step 1 Step 2 Step 3

18. GIS Data Sources Existing data Digital Map and Plan Paper Files Low Cost Acquisition Remote Sensing Photogrammetry Field Survey High Cost

19. Geospatial Analysis Geography + GIS = Geospatial An approach to applying statistical methods and other informational techniques to data which has a geographical or geospatial aspect Such analysis would typically employ software capable of geospatial representation and processing, and apply analytical methods to terrestrial or geographic datasets, including the use of GIS

20. Operations Surface analysis In particular analyzing the properties of physical surfaces, such as gradient, aspect and visibility, and analyzing surface-like data “fields” Network analysis Examining the properties of natural and man-made networks in order to understand the behavior of flows within and around such networks; and locational analysis Geovisualization The creation and manipulation of images, maps, diagrams, charts, 3D views and their associated tabular datasets

21. Conclusion GIS is a broad term that can refer to a number of different technologies, processes, and methods It is attached to many operations and has many applications related to engineering, planning, management, transport/logistics, insurance, telecommunications, and business Modern GIS technologies use digital information, for which various digitized data creation methods are used Many disciplines benefit from GIS