Download presentation
Presentation is loading. Please wait.
1
"GIS Concepts"
2
GIS Definition Many expert used GIS for his own demand and that is the reason that they define GIS in that context. Aronoff (1989) gives a general description of GIS as “any manual or computer-based set of procedures used to store and manipulate geographically-referenced data.” More specifically, Aronoff (1989) defines GIS as "a computer-based system that provides four sets of capabilities to handle georeferenced data: i) data input ii) data management (data storage and retrieval) iii) manipulation and analysis iv) data output.” Cower (1988) defines GIS as “a decision support system involving the integration of spatially referenced data in a problem solving environment”.
4
COMPONENTS OF GIS Hardware Software
Several components are involved in GIS technology. Hardware A computer and the associated accessories are essential for handling spatial data in GIS. These devices are collectively known as hardware like scanners, CPUs, Digitizers, Workstations & plotters etc. Software Software refers to the programmes that run on computers; these include programmes to manage the computer and to perform specific functions. For example, DBMS, Corel draw, ILWIS, Arc/view, Mapinfow, ERDAS Imagine, IDRISI and Arc/info are specialised software programmes designed to perform certain tasks. Continued………
5
Human Input (live ware)
Database A central theme to GIS is the database. A GIS database deals with spatial data. GIS facilitate integration of spatial and attribute data and this makes GIS unique in contrast to other database systems. The beauty of GIS technology lies in the ability to assimilate divergent sources of data and analyse them. Human Input (live ware) People who work with GIS form the most important component. GIS constitute truly a interdisciplinary field and require varied backgrounds of expertise, depending upon the applications. In addition, for technical management, a Hardware Specialist, System Administrator, and Database Manager are required for corporating the GIS set-up. Policy and Procedures A methodology is must to derive the results users need. Basically, this includes spatial analysis for the particular application. By and large, this depends upon the institutional framework and its interest in exploiting GIS technology for decision-making
6
Geographic Information Systems
IDRISI ILWIS ARC/ INFO PEOPLE GIS SOFTWARE POLICY AND PROCEDURES FOR RESOURCE MANAGEMENT HARDWARE DATA
7
GIS Historical Development
CAD/CAM Military Studies Cartography Remote Sensing Spatial Mathematics Urban Planning Geography Computer Science Earth Science Surveying and Photogrammetry Civil Engineering GIS Historical Development
9
Components of GIS + GIS ABSTRACTION OR SIMPLIFICATION USERS SOFTWARE
DATABASE TOOLS THE REAL WORLD RESULTS
10
FOUR Ms Modeling Measurements Mapping Monitoring Time-1 Time-2 Time-3
Landuse Soil Topography GEOGRAPHIC INFORMATION SYSTEM The four Ms. Measurement, Mapping, Monitoring and Modeling of environmental features and processes can be enhanced through the use of a GIS Adapted from J.Stars and J.Estates Time-1 Time-2 Time-3 Updating Spatial Analyses
11
GIS Hydrology Landuse Districts Topography Soils
A computer based system capable of holding and using data describing places on the earth’s surface The real world consists of many geographies which can be represented as a number of related data layers. Hydrology Landuse Districts Topography Soils GIS GIS IS SUPPORTING TOOL FOR DECISION MAKERS
12
HOW GIS WORKS GIS operations Geology Hydrology Thematic object
Point Area Line -Analysis Cartographic processing .- Generalization - Symbolization Thematic object selection Hydrology Soil Attribute tables Aerial photographs Satellite images Field Survey GPS Statistical tables Maps Real world Decision makers
13
Topographic REAL-WORLD Contour lines Parcels MAPS AND SPATIAL DATA
14
Questions a GIS can answer
Location Condition Trends Patterns Modelling
19
Geographic Data
20
Types of GIS Vector GIS Raster GIS Hybrid GIS
Technology is moving towards hybrid GIS Raster Vector Integration
21
Vector Representation
The Vector Data Model Features of Spatial Object Points (Example : Location of house) Lines(Example : Railway) Polygons (Examples : Forest area) The location of features on the earth’s surface are referred to map positions using an XY coordinate system (termed a Cartesian Coordinate System). PointA Singly XY pair LineSeries of XY pair PolygonA closed loop of XY coordinate pairs that define the boundary
22
Raster Representation
Row Column Cell Size Resolution Buildings Road River
23
Attribute Data District Name Area Population
Peshawar 395 sq. km. 6,75,341 Swabi 385 sq. km. 2,57,086 Dir lower 119 sq. km. 1,72,952 Industry Information Industry Information Agriculture Census Education and Health
24
SPATIAL AND NON-SPATIAL DATA
City blocks Land use 001 Institutional 002 Commercial 003 Commercial 004 Residential 005 Residential 006 Residential 007 Industrial 008 Residential 009 Industrial 010 Industrial 011 Residential 012 Industrial 013 Residential 014 Residential 015 Residential Map: City blocks NON-SPATIAL DATA SPATIAL DATA
25
THEN WHAT SHOULD BE THE BEST ROUTE, LEAVE IT UPTO GIS
Analysis Analysis Cadastral parcel Alternative 1 Alternative 3 Alternative 2 National park Risk area Land-use Soil Slopes Digital Terrain Model Decision makers Topography
26
Four Major GIS Functions
Ÿ data capture - graphic data: digitised, converted from existing data - attribute data: keyed-in, loaded from existing data files Ÿ data storage and manipulation - file management - editing Ÿ data analysis - database query - spatial analysis - modelling Ÿ data display - maps - reports
27
1.INPUT OF DATA WHAT ARE THE FUNCTIONS INVOLVED IN GIS Data collection
(Both Geographical & Statistical) Data verification Data transfer Data editing
28
2.DATA STORAGE WHAT ARE THE FUNCTIONS INVOLVED IN GIS On hard disk
On floppy disk On CDs
29
3.MANIPULATION OF DATA WHAT ARE THE FUNCTIONS INVOLVED IN GIS
Cartographic function a.Scale changes b.Vector-Raster changes c.Projection changes d.Map embellishment like adding north, title, scale and legend etc (continued….)
30
3.MANIPULATION OF DATA WHAT ARE THE FUNCTIONS INVOLVED IN GIS
Data integration (Core of GIS) a.Maps over laying b.Spatial transformation c.Spatial aggregation (continued……..)
31
HOW G.I.S. WILL ANALYSE THE DATA
Example: Selection of waste disposal site for Peshawar city under the following conditions 1. The selected site should be located within 20 km distance from the city center, but further than 300 meters from any existing built-up area. 2. The site should be located on clay-rich soils, with a maximum thickness of 5 meters and clay content greater than 50%. 3. The site should have an area of at least 2 hectares. (Continue…..)
32
HOW G.I.S. WILL ANALYSE THE DATA
Example: Selection of waste disposal site for Peshawar city under the following conditions 4. Should have an area, which do not have an important economic or ecological value. 5. Site should be located on a terrain with slope less than 20 degree to prevent erosion and to assure accessibility. 6. Should be free from active landslides.
33
HOW G.I.S. WILL ANALYSE THE DATA
Following data are available for data input a. Contour map indicated in degrees b. Landuse map c. Road map d. Slide map with landslide distribution e. City map f. Geological map FORMULAS WILL BE USED AS Lslide=iff((slide=“dormant”)or(slide=“active”),1,0) Luse=iff((landuse=“barren”)or(landuse=“forest”),1,0)
34
SELECTION OF SUITABLE SITE
FOR WASTE DISPOSAL
35
3.MANIPULATION OF DATA WHAT ARE THE FUNCTIONS INVOLVED IN GIS
Feature measurement a.Number of features b.Calculate distance, area c.Statistical analysis like crossing of tables and correction
36
4.DATA OUTPUT WHAT ARE THE FUNCTIONS INVOLVED IN GIS Data presentation
a.Maps b.Tables c.Diagrams DATA TRANSFERING/DATA SHARING
37
Principal Components and Functions of an Ideal GIS
38
YOU SHOULD BE CLEAR IN MIND WHILE ENTERING DATA INTO COMPUTER
"Rubbish in" "Rubbish out"
39
GEOGRAPHIC DATA Spatial and Non-Spatial data
There are two important components of geographic database: its geographic position and its attributes or properties. In other words, spatial data (where is it?) and attribute data (what is it?) Analogue Data: A physical product displaying information visually on paper like maps, aerial photos, imageries, tabular data and written report etc. Digital Data: Information derived from computer
40
Basic types of spatial Data
Maps model the real world with points, lines, and polygons. Symbols and labels describe the descriptive information about the geographic features. Points Points define the discrete locations of geographic features which are too small to illustrate as lines or polygons such as well or telephone poles. Points can be used to illustrate the locations of mountain peak or discrete elevation points. Lines Lines represent the linear features of geographic object too narrow to illustrate as polygons, such as streets and streams that have length but no area. Moreover, contour lines are represented as the lines By using different symbols and labels, descriptive information of linear features are illustrated. For example: Roads are drawn with various line widths and patterns and colors to represent different road types, e.g., highway as wide solid red colour line, blue lines are used to illustrate the streams. The symbol can be used to illustrate the railway. City streets are labeled with names and often address ranges.
41
Polygons Polygons are closed features that represent the shape and location of homogeneous features such as landuse, forest types. Tone of the colour can be applied to illustrate the density of population, green color can be used to represent vegetation and blue colour can be used to illustrate lake. Surfaces A surface represents the elevation, presence or absence of something for every point on the piece of earth. The elevation models are best examples to illustrate as the surfaces. Surfaces are typically represented on the maps as the series of isolines. Elevation contours, rainfall, temperature can be represented as the surface of isolines. Surfaces can be represented as the Raster Elevation Model and Vector Elevation Model.
42
Geometry of Spatial Data
Point Line Area surface
43
REPRESENTATION OF GEOGRAPHIC DATA
Vector Graphics: Images are built-up from points, lines(segments) and areas (Polygons). Each defined by pair of X-Y co-ordinates. Preparing a map by digitization is converted into vector data in computer. Raster Graphics: Images are built-up from cells which is called as Pixels. In raster graphics, the smaller the area of land that each cell represents, the higher the resolution of the data and higher the spatial accuracy, ultimately the larger the files needed to store the data.
45
SPATIAL DATA INPUT Scanning (automatic digitizing) Manual digitizing
X Y Scanning (automatic digitizing) Editing Raster model Improving Vectorizing Apply attributes Sensor X Y Manual digitizing Improving Apply attributes Vector model Digital Landscape Model
47
Features Raster model)
48
Advantages and Disadvantages of the Raster and Vector Data Models
RASTER MODEL VECTOR MODEL Advantages - easy and efficient overlaying compatible with RS imagery same grid cells for several attributes Disadvantages inefficient use of computer storage errors in perimeter, area, and shape difficult network analysis inefficient projection transformations loss of information when using large cells less accurate (although attractive) maps - efficient for network analysis - efficient projection transformation - accurate map output - complex data structure - difficult overlay operations - not compatible with RS imagery
49
APPLICATION OF GIS Some typical examples of GIS applications are;
Canada was the pioneer in development of GIS as a result of innovations dating back to the early 1960s. Much of the credit goes to Roger Tomilson for the early development of GIS. Although the field of GIS has been around for the last 25 years the real potentials have become apparent only since the late 1980s. Afterwards widely used in USA, Canada & Western Europe. Some typical examples of GIS applications are; land-use planning and management e.g. Cadestral mapping, Urban growth, Landuse changes etc. S.O.P, SUPARCO, P.D.A, C.D.A, P.E & D) oil & mineral exploration (O.G.D.C, Oil companies, P.G.S) environmental impact studies management of water resources (IIMI, AKRSP, WAPDA) natural hazard mapping (FFC, NESPAK) forestry and wildlife management (FMC, PFI, AKRSP) soil degradation studies (Soil survey of Pakistan) monitoring desertification agricultural development socio-economic survey and mapping (S.O.P & Primary education project in NWFP, Baluchistan, Sind, N.As & A.K.)
52
SELECTION OF SUITABLE ROUTE BETWEEN PESHAWAR AND KOHAT
Recreational park ? ? ? ? ? Swamp Private Parcel ? ? ? ? ? Bara River ? ? ? ?
Similar presentations
© 2025 SlidePlayer.com Inc.
All rights reserved.