2. INTRODUCTION TO GIS  Used to describe computer facilities which are used to handle data referenced to the spatial domain.  Has the ability to inter- relate datasets and to carry out functions to improve their analysis and the presentation of the results.

3. DEFINITON OF GIS  GIS is defined as “ a set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes.”  A computerized system for capturing, checking, manipulating analyzing and displaying data related to positions on or near the earth’s surface.

4. EVOLUTION (from mapping to GIS)  Topological technique permitted the data not only to determine where a point or a line or an area was located but also to analyze those features.  GIS data can be assembled by -existing databases -digitized or scanned from existing maps -GPS surveying techniques

5. DEVELOPMENT WITH MODERN GIS  Modern GIS developments are based on a data theory.  There are several aspects are considered: GIS specific characteristic a) location-coordinates and street address b) attributes-features that being analyzed  GIS activities can be by two board field a) geographic b) cultural

6. ADVANTAGES of GIS  Storage and easily update data  Sort and store spatial features  Allow to zoom into section of data to graphic and text which may be hidden  Analyze both entities and data using sophisticated computer programs  Allow user to prepare maps

7.  Allow user to use data to prepare maps at different scales  Allow to import stored data electronically and save the cost of collecting data  Build and augment a database  Create new maps by modeling or reinterpreting existing data

8. COMPONENTS OF A GIS  It can be divided into 4 major activities: - Data collection and input. - Data storage and retrieval. - Data analysis. - Data output and display.

9. GIS FUNCTIONAL ELEMENTS Analogue Data Collection and Input Digital Data Storage and Management Data Retrieval Data Manipulation and Analysis Data Display Image Copy Hard Copy

10. GIS TYPICAL COMPONENTS:  The computer with GIS software is the main component and typically uses Microsoft or Unix operating systems.  Data collection can be divided into geometrics components that are: - Field surveying, - Remote sensing, - Digitalization of existing maps and plans, - Digital data transfer via Internet or CD/DVD

11.  Computer storage: - Hard disks, - Optical disks etc.  Software designed are to download, edit, sort and analyze data.  It also designed to process and present data in the form of graphics and maps and/or plans.

12. SOURCES FOR GIS DATA:  The most important part of GIS is the collection of data.  If data can be obtained from other sources, the efficiency of the process increases.  Traditional sources for data collection: - Field surveying. - Remotely sensed images. - Existing topographic maps, plans etc. - Electronic transfer of previously digitalized data from Government agencies or commercial firms.

13. DATA SOURCES GIS DATA SOURCES: Structural, Construction, Hydrology, Environmental. DATA MANIPULATI ON: Highway design, Site planning, Landscape planning, Drainage analysis.

14. DATA CATEGORISATION Node ArcPolygon pointIndependent arcIndependent single polygon Independent multiple polygon point with vertical information Independent multiple arcs Contiguous polygon Point in polygon arc junctionConnected arcs network overlapnoncontiguou s

15. GIS DATA STRUCTURE  GIS data structure can be divided into Spatial data Attribute data

16. GIS DATA STRUCTURE Spatial Vector data format - positional data is represented in form of coordinates Raster data format – consists of a set or matrix of cells or pixels of a specific size and area. Attribute Digital data - record data by using computer software. Example computer programming Non- Digital date – record data by writing manually. Example file.

18. vector data format,  In vector data format, the basic unit of spatial information are points, lines and areas.  Each units is composed as a series of one or more coordinate points.  By using vector systems, there are 3 types of objects possible: Nodes Arcs Polygons VECTOR DATA FORMAT

19. RASTER DATA FORMAT  Consists of a set or matrix of cells or pixels of a specific size and area.  The image represent a scanned map or an aerial photograph of the site to be modeled.  Point is represented by a single grid cell, a line by consecutively neighboring cells and an area by a cluster of neighboring cells.  Can be for merging and investigating the vectorising method for a specific purpose Example : raster image with a vector image for movement of river

20. COMPARISON OF VECTOR AND RASTER VECTOR DATARASTER DATA Represent feature shape more accurately Rectangular representation and more generalized. Represent feature with well- defined boundaries. Represent a more generalized view. Compact data structure represented by simple points, lines and polygons with topological relationship. The data structure relatively simple. It uses rows and column of grid cell having uniform size. Resolution of data depends on compilation method and scale of source data. The data resolution depends on the cell size. Easy to represent topological relationships.Difficult to represent topological relationships.

21. GEOREFERENCING:  Most geographic data users have the same earth- reference techniques that the data can be shared by using various computer systems.  Coordinate Grids: The plane coordinate grid systems 1983 (SPCS83) has been applied to all states. Software programs readily convert coordinates based on one projection.

22.  Transformation: If a GIS is tied to a specific coordinate grid and orientation, the new data needs to be transformed to fit the working model.  Transformations can be made in: - Grid reference, - Scale - Orientation.  The computer programs designed to translate from one grid reference to another, convert the scale, and rotate to appropriate orientation.

23. DATABASE MANAGEMENT:  To organize the data so that the information about entities and their attributes can be accessed by rapid computerized search and retrieval techniques.  Data collections can range in complexity.