1.gis

www.mcsmapping.com August 25, 2010

Presentation Outline

• History
• Definition
• Components
GIS • Applications
Fundamentals • Data models
• Raster Data
• Vector Data

© Magendhiran Consultancy Services. All rights reserved. www.mcsmapping.com 8/25/2010 1 © Magendhiran Consultancy Services. All rights reserved. www.mcsmapping.com 8/25/2010 2

Where did GIS come from? A Brief History of GIS
• GIS is built upon knowledge from geography, • GIS’s origins lie in thematic cartography (manual map overlay)
• Computer cartography advances in 1950s and 1960s
cartography, computer science and mathematics • Early influential data sets were the World Data Bank and the
• Geographic Information Science is a new GBF/DIME files. Early systems were CGIS, MLMIS, GRID and LUNR
• The Harvard University ODYSSEY system was influential due to its
interdisciplinary field built out of the use and topological arc-node (vector) data structure
theory of GIS • GIS was significantly altered by (1) the PC and (2) the workstation
• During the 1980s, new GIS software could better exploit more
advanced hardware
• User Interface developments led to GIS's vastly improved ease of
use during the 1990s
• During the 1980s, new GIS software could better exploit more
advanced hardware

© Magendhiran Consultancy Services. All rights reserved. www.mcsmapping.com © Magendhiran Consultancy Services. All rights reserved. www.mcsmapping.com

Defining GIS Geographic Information Systems (GIS)
• Different definitions of a GIS have evolved in different • The common ground between information processing
areas and disciplines and the many fields using spatial analysis techniques.
(Tomlinson, 1972)
• All GIS definitions recognize that spatial data are unique
because they are linked to maps (Space matters!) • A powerful set of tools for collecting, storing, retrieving,
transforming, and displaying spatial data from the real
• A GIS at least consists of a database, map information, world. (Burroughs, 1986)
and a computer-based link between them • A computerized database management system for the
capture, storage, retrieval, analysis and display of spatial
data. (NCGIA, 1987)
• A decision support system involving the integration of
spatially referenced data in a problem solving
environment. (Cowen, 1988)

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An Inelegant Definition for GIS GIS: intuitive description
A system of integrated computer-based tools for end-to- • A map with a database behind it.
end processing (capture, storage, retrieval, analysis, • A virtual representation of the real world and its
display) of data using location on the earth’s surface for infrastructure.
interrelation in support of operations management, • A consistent “as-built” of the real world, natural and
decision making, and science. manmade
Which is
• set of integrated tools for spatial analysis • queried to support on-going operations
• encompasses end-to-end processing of data(capture, • summarized to support strategic decision making and
storage, retrieval, analysis/ modification, display) policy formulation
• uses explicit location on earth’s surface to relate data • analyzed to support scientific inquiry
• aimed at decision support, as well as on-going
operations and scientific inquiry

Why Study GIS? The major areas of GIS application
• 80% of local government activities estimated to be geographically based • Local Government
– plats, zoning, public works (streets, water supply, sewers), garbage – Public works/infrastructure management (roads, water, sewer)
collection, land ownership and valuation
– Planning and environmental management
• a significant portion of state government has a geographical component
– natural resource management – property records and appraisal
– highways and transportation • Real Estate and Marketing-Retail site selection, site evaluation
• businesses use GIS for a very wide array of applications • Public safety-Crime analysis, fire prevention, emergency
– retail site selection & customer analysis management
– logistics: vehicle tracking & routing • Natural resource exploration/extraction - Petroleum, minerals,
– natural resource exploration (petroleum, etc.) quarrying
– precision agriculture
• Transportation- Airline route planning, transportation modeling
– civil engineering and construction
• scientific research employs GIS • Public health and epidemiology
– geography, geology, botany • The Geospatial Industry - Data development, application
– anthropology, sociology, economics, political science development, programming
– Epidemiology, criminology


Advantages of GIS Examples of Applied GIS
1. The potential and substantial benefits of using GIS make it a very • Urban Planning, Management & Policy
important tool making the work of any organization easier and more – Zoning, subdivision planning
– Land acquisition
productive. Some of the potential benefits of GIS are: – Economic development
2. Opportunity to reduce sets of manual maps held and associated storage – Code enforcement
costs. – Housing renovation programs
3. Faster and more extensive access to geographic information. – Emergency response
– Crime analysis
4. Improved analysis e.g. Of areas, distances, patterns, etc. – Tax assessment
5. Better communication of information to public officers, members. • Environmental Sciences
– Monitoring environmental risk
6. Improved quality of services. – Modeling storm water runoff
7. Better targeting and coordination of services. – Management of watersheds, floodplains, wetlands, forests,
8. Improved productivity in providing public information. aquifers
– Environmental Impact Analysis
9. Improved efficiency in updating maps. – Hazardous or toxic facility sites
10. The ability to track and monitor growth and development over time – Groundwater modeling and contamination tracking
11. Improved ability to aggregate data for specific sub areas. • Political Science
– Redistricting
12. Thus GIS's have become indispensable tools for governance, commerce, – Analysis of election results
and environmental and social science. – Predictive modeling


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Examples of Applied GIS contd. Components of GIS
•Civil Engineering/Utility
•Locating underground facilities
•Designing alignment for freeways, transit
•Coordination of infrastructure maintenance
• Business
•Demographic Analysis
•Market Penetration/ Share Analysis
•Site Selection
•Education Administration
• Attendance Area Maintenance
• Enrollment Projections
• School Bus Routing
•Real Estate
•Neighborhood land prices
•Traffic Impact Analysis
•Determination of Highest and Best Use
•Health Care
•Epidemiology
• Needs Analysis
• Service Inventory


GIS System Architecture and Components The GIS Data Model: Implementation
Administrative Boundaries
Utilities
Data Input
Zoning
Buildings
Parcels
Geographic
Query Input Hydrography
Database Streets
Digital Orthophoto

• Data is organized by layers, coverages or themes (synonomous
Output: Display Transformation concepts), with each layer representing a common feature.
and Reporting and Analysis
• Layers are integrated using explicit location on the earth’s
surface, thus geographic location is the organizing principal.


The GIS Model: example The GIS Model: example


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The GIS Model: example Spatial and Attribute Data
Here we have three layers or themes:
• Spatial data (where)
--roads, – specifies location
roads --hydrology (water), – stored in a shape file or similar geographic file
--topography (land elevation)
longitude They can be related because precise geographic
• Attribute (descriptive) data (what, how much, when)
coordinates are recorded for each theme. – specifies characteristics at that location, natural or human-
created
Layers are comprised of two data types
– stored in a data base table
hydrology •Spatial data which describes location (where)
•Attribute data specifying what, how much, when • GIS systems traditionally maintain spatial and attribute data
longitude separately, then “join” them for display or analysis
Layers may be represented in two ways: – for example, in QGIS, the Attributes of … table is used to join
•in vector format as points and lines a shapefile (spatial structure) with a data base table containing
•in raster(or image) format as pixels attribute information in order to display the attribute data
topography
spatially on a map
All geographic data has 4 properties:
projection, scale, accuracy and resolution
longitude

Representing Data Concept of Vector and Raster
Real World
Raster Model
• area is covered by grid with (usually) equal-sized, square cells
• attributes are recorded by assigning each cell a single value based on the
majority feature (attribute) in the cell, such as land use type.
• Image data is a special case of raster data in which the “attribute” is a
reflectance value from the geomagnetic spectrum
– cells in image data often called pixels (picture elements)
Raster Representation Vector Representation
Vector Model 0 1 2 3 4 5 6 7 8 9
0 R T point
The fundamental concept of vector GIS is that all geographic features in the real
1 R T
work can be represented either as: 2 H R
• points or dots (nodes): trees, poles, fire plugs, airports, cities 3 R line
• lines (arcs): streams, streets, sewers, 4 R R
5 R
• areas (polygons): land parcels, cities, counties, forest, rock type 6 R T T H
Because representation depends on shape, QGIS refers to files containing vector 7 R T T polygon
data as shapefiles 8 R
9 R

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Raster & Vector Data The key properties of spatial data
Advantages of raster data • Projection: the method by which the curved 3-D surface of the
1. Simple data structure earth is represented by X,Y coordinates on a 2-D flat map/screen
2. Easy and efficient overlaying – distortion is inevitable
3. Compatible with RS imagery • Scale: the ratio of distance on a map to the equivalent distance on
4. High spatial variability is efficiently represented the ground
5. Simple for own programming – in theory GIS is scale independent but in practice there is an
6. Same grid cells for several attributes implicit range of scales for data output in any project
• Accuracy: how well does the database info match the real world
Advantages of vector data – Positional: how close are features to their real world location?
1. Compact data structure – Consistency: do feature characteristics in database match
2. Efficient for network analysis those in real world -is a road in the database a road in the real
world?
3. Efficient projection transformation
– Completeness: are all real world instances of features present
4. Accurate map output.
in the database? - Are all roads included.
• Resolution: the size of the smallest feature able to be recognized
– for raster data, it is the pixel size

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