WHAT IS GIS? By Okan Fistikoglu

DEFINITION Geographical Information Systems (GIS) are the systems that store, retrieve, analyze, transform and display geo-coded spatial and attribute data. What is geo-coded data?

GEOCODED DATA =Geodata Position (x,y,z) Shape Type (Point, Line, Polygon) Relation to others (Topology) Thematic Content (Indicated Info) SPATIAL DATA ATTRIBUTE DATA

GEOCODED DATA =Geodata more examples?

COMPONENTS OF A GIS Geographical Information Systems have three important components, 1. computer- hardware 2. sets of application software modules 3. a proper organizational context. These three components must be in balance if the system is to function satisfactorily.

COMPONENT-1 computer- hardware DIGITIZER SCANNER C.P.U. DISC DRIVER PLOTTER SCREEN TAPE DRIVER

COMPONENT-2 application software The software package for geographical information system consists of five basic technical modules. Data Input Query Input Geo Database Display and Reporting Transformations

COMPONENT-2 application software Data Input Query Input Geo Database Display and Reporting Transformations Existing mapsObservations Sensors Magnetic media Interactive terminal Text files Digitizers Scanners DATA INPUT

COMPONENT-2 application software Data Input Query Input Geo Database Display and Reporting Transformations GEOGRAPHIC DATABASE Position TopologyAttributes Management System Input Query Input Retrieval Transinformation

COMPONENT-2 application software Data Input Query Input Geo Database Display and Reporting Transformations MAPS TABLESFIGURES Magnetic media Visual Display terminal Plotter Printer DISPLAY AND REPORTING

COMPONENT-2 application software Data Input Query Input Geo Database Display and Reporting Transformations TRANSFORMATION Maintenance Utilization and Analysis

COMPONENT-3 organizational contex Management Aims and Queries from management Information for Management Geographical Information System Data Gathering

TYPE OF GEODATA Position (x,y,z) Shape Type (Point, Line, Polygon) Relation to others (Topology) Thematic Content (Indicated Info) SPATIAL DATA ATTRIBUTE DATA REMEMBER!!!

ATTRIBUTE DATA (Thematic Content) Alfanumeric Value (String) =  “Okan Fistikoglu” “1. Kordon Street” “Forest” Numeric Value  ≤ ≥       Birth “1971” No. “256” Percent “35” Type Permisible Operations Examples

SPATIAL DATA X, Y, Z coordinates of the dataPosition Shape Topology Types Point, Line, Polygon Positional relation of the data to the others Vector, Raster NEW

STRUCTURE OF SPATIAL DATA Analysis of attributes and their interactions within the region investigated can be performed using two different approaches. These two approaches determine the process of data collection, data manipulation, and consequently, determine the Structure of Spatial Data. Accordingly, there are two types of structures: (a)vector structure (b)raster or grid structure. VECTOR RASTER

VECTOR STRUCTURE X COORDINATE Y COORDINATE ATTRIBUTE 1 ATTRIBUTE WELL30m POINT X Y

VECTOR STRUCTURE NODEXY LINEFROM NODE TO NODE ATTRIBUTE 11250m m

VECTOR STRUCTURE NODEXY LINEFROM NODE TO NODE LEFT POLY RIGHT POLY ATTRIBUTE 0URBAN 1PARK 2HOUSE

RASTER STRUCTURE POINT LINE POLYGON =WELL 4=ROAD WIDTH 4=FOREST 5=URBAN

VECTOR vs RASTER Some major strengths and limits of vector and raster structures. VECTORRASTER Storage efficiency goodpoor Storage data structure complexsimple Spatial sampling varying across study arearegular across study area Spatial measures preciseapproximate Spatial relationships complex to handleeasy to handle Multi-attribute analysis complexsimple