5. Geographic Information System
• Geographic – 80% of government data collected is associated
with some location in space
• Information - attributes, or the
characteristics (data), can be used to symbolize and provide
further insight into a given location
• System – a seamless operation linking the information to the
geography – which requires hardware, networks, software,
data, and operational procedures
…not just software!
…not just for making maps!
6. • Many More to Come…
Environmental impact assessment
Resource management
Land use planning
Tax Mapping
Water and Sanitation Mapping
Transportation routing
And many more ...
GIS Operations -
7. How does a GIS work?
• GIS data has a spatial/geographic
reference
This might be a reference that describes a
feature on the earth using:
• a latitude & longitude
• a national coordinate system
• an address
• a district
• a wetland identifier
• a road name
8. Types of data
Two types of data are stored for each item in the
database
• 1. Attribute data:
Says what a feature is
• Eg. statistics, text, images, sound, etc.
• 2. Spatial data:
Says where the feature is
This also of two types -
1. Vector data
2. Raster data:
11. • A GIS stores information about the world as a
collection of thematic layers that can be linked
together by geography
Polygon 3 Scrub 17 Very high Clay
Geography and Databases
12. GIS provides Data Integration
Vectors
Topology
Networks
Terrain
Surveys
Images
CAD
Drawings
Annotation
Addresses
27 Main St.
Attributes
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107’
3D Objects
Dimensions
• Roads
• Land Parcels
• Population
• Utilities
• Land Mines
• Hospitals
• Refugee Camps
• Wells
• Sanitation
13.
14. Data formation in GIS
Capturing data
Scanning: all of map converted into raster data
Digitising: individual features selected from map as
points, lines or polygons
Geo-referencing
Initial scanning digitising gives co-ordinates in inches
from bottom left corner of digitiser/scanner
Real-world co-ordinates are found for few
registration points on the captured data
These are used to convert the entire map onto a
real-world co-ordinate system