DEFINITION : GIS is a powerful set of tools for collecting, storing , retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes APPLICATION AREAS OF GIS Agriculture Business Electric/Gas utilities Environment Forestry Geology Hydrology Land-use planning Local government Mapping 11. Military 12. Risk management 13. Site planning 14. Transportation 15. Water / Waste water industry COMPONENTS OF GIS DATA INPUT SPATIAL DATA MODEL Data Model: It describes in an abstract way how the data is represented in an information system or in DBMS Spatial Data Model : The models or abstractions of reality that are intended to have some similarity with selected aspects of the real world Creation of analogue and digital spatial data sets involves seven levels of model development and abstraction SPATIAL DATA MODEL Conceptual model : A view of reality Analog model : Human conceptualization leads to analogue abstraction Spatial data models : Formalization of analogue abstractions without any conventions Database model : How the data are recorded in the computer Physical computational model : Particular representation of the data structures in computer memory Data manipulation model : Accepted axioms and rules for handling the data SPATIAL DATA MODEL SPATIAL DATA MODEL Objects on the earth surface are shown as continuous and discrete objects in spatial data models Types of data models Raster data model vector data models RASTER DATA MODEL Basic Elements : Extent Rows Columns Origin Orientation Resolution: pixel = grain = grid cell Ex: Bit Map Image (BMP),Joint Photographic Expert Group (JPEG), Portable Network Graphics(PNG) etc RASTER DATA MODEL VECTOR DATA MODEL Basic Elements: Location (x,y) or (x,y,z) Explicit, i.e. pegged to a coordinate system Different coordinate system (and precision) require different values o e.g. UTM as integer (but large) o Lat, long as two floating point numbers +/- Points are used to build more complex features Ex: Auto CAD Drawing File(DWG), Data Interchange(exchange) File(DXF), Vector Product Format (VPF) etc VECTOR DATA MODEL RASTER vs VECTORRaster is faster but Vector is corrector TESSELLATIONS OF CONTINUOUS FIELDS Triangular Irregular Network: (TIN) TIN is a vector data structure for representing geographical information that is continuous Digital elevation model TIN is generally used to create Digital Elevation Model (DEM) DIGITAL ELEVATION MODEL DATA STRUCTURES Data structure tells about how the data is stored Data organization in raster data structures Each cell is referenced directly Each overlay Is referenced directly Each mapping unit is referenced directly Each overlay is separate file with general header