2. DEFINITION OF GIS ?
A geographic information system (GIS) is a computer
system for capturing , storing , querying , analyzing and
displaying geospatial data.
Geographic Information Systems is a computer-based tool
that analyzes, stores, manipulates and visualizes
geographic information, usually in a map.
3. FIVE COMPONENTS OF GEOGRAPHIC
INFORMATION SYSTEM (GIS)
1. Hardware:
2. Software:
3. Data:
4. People:
5. Methods:
4. COMPONENTS OF GIS:
1.Hardware:
Hardware is Computer on which GIS software runs. Nowadays there
are a different range of computer, it might be Desktop or server
based. ArcGIS Server is server based computer where GIS
software runs on network computer or cloud based.
Some of the hardware components are:
Motherboard, Hard driver, processor, graphics card, printer and so
on.
5. COMPONENTS OF GIS:
2.Software:
Next component is GIS software which provide tools to run and edit spatial
information. It helps to query, edit, run and display GIS data.
Some of the software components are:
GIS Tools
RDBMS
GUI:
Query Tools
Layout:
6. 3.data
The most important and expensive component of the Geographic
Information System is Data which is generally known as fuel for GIS.
GIS data is combination of graphic and tabular data. Graphic can be
vector or raster. Both type of data can be created in house using GIS
software or can be purchased. The process of creating the GIS data
from the analog data or paper format is called digitization.
GIS Data two Types:
Raster: Raster image store information in a cell based manner. It can
be aerial photo, satellite image, Digital Elevation Model (DEM). Raster
images normally store continuous data.
Vector: Vector data are discrete. It store information in x, y coordinate
format. There are three types of Vector data: Lines, Points and Area
COMPONENTS OF GIS:
7. COMPONENTS OF GIS:
4.People:
People are user of Geographic Information System. They run the GIS
software. Hardware and software have seen tremendous development
which made people easy to run the GIS software.
5.Method
For successful GIS operation a well-designed plan and business
operation rules are important. Methods can vary with different
organizations. Any organization has documented their process plan for
GIS operation. These document address number question about the GIS
methods: number of GIS expert required, GIS software and hardware,
Process to store the data, what type of DBMS (database management
system) and more. Well designed plan will address all these question.
8. FUNCTIONS OF GIS
The Functions of GIS describe the steps that have to be taken to
implement a GIS. These steps have to be followed in order to obtain a
systematic and efficient system. The steps involved are:
GIS functions:
I) Data Capture.
II) Data Compilation.
III) Data Storage (GIS Data Models).
IV) Manipulation.
V) Analysis.
9. FUNCTIONS OF GIS
I) Data Capture.
Data used in GIS often come from many sources. Data sources are
mainly obtained from Manual Digitization and Scanning of aerial
photographs, paper maps, and existing digital data sets. Remote
sensing satellite imagery and GPS are promising data input sources for
GIS.
Digitization; A conversion process which converts paper maps into
numerical digits that can be stored in the computer. Digitizing simplifies
map data into sets of points, lines, or cells that can be stored in the GIS
computer.In this stage Digitization is carried out. There are two basic
methods of Digitization: Manual Digitizing & Scanning
10. FUNCTIONS OF GIS
II) Data Compilation
Following the digitization of map features, the user completes the
compilation phase by relating all spatial features to their respective
attributes, and by cleaning up and correcting errors introduced as a
result of the data conversion process.The end results of compilation is a
set of digital files, each accurately representing all of the spatial and
attribute data of interest contained on the original map manuscripts.
These digital files contain geographic coordinates for spatial objects
(points, line polygons and cells) that represent mapped features.
11. FUNCTIONS OF GIS
III) Data Storage (GIS Data Models).
Once the data have been digitally compiled, digital map files in
the GIS are stored on magnetic or other digital media. Data
storage is based on a Generic Data Model that is used to convert
map data into a digital form.
The two most common types of data models are Raster and
Vector. Both types are used to simplify the data shown on a map
into a more basic form that can be easily and efficiently stored in
the computer.
12. FUNCTIONS OF GIS
IV) Manipulation.
Once data are stored in a GIS, many manipulation options are
available to users. These functions are often available in the form
of "Toolkits." A toolkit is a set of generic functions that a GIS user
can employ to manipulate and analyze geographic data. Toolkits
provide processing functions such as data retrieval measuring
area and perimeter, overlaying maps, performing map algebra,
and reclassifying map data.
Data manipulation tools include Coordinate change,
Projections, and Edge matching, which allow a GIS to
reconcile irregularities between map layers or adjacent map
sheets called Tiles.
13. FUNCTIONS OF GIS
V) Analysis.
(i) Spatial analysis, eg connectivity, proximity, contiguity,
intervisibility, digital terrain modelling.
(ii) Statistical analysis, eg histograms, correlation,
measures of dispersion, frequency analysis.
(iii) Measurement, eg line length, area and volume
calculations, distance and directions.
14. TYPES OF GIS
This course will cover three groups GIS:
Web-based GIS:ONS and London profiler.
Geo-browser: Google earth.
Dextop GIS: Arc GIS.
16. DATA STRUCTURES
o Representing Geographic Features:
by recognizing two types of data:
Spatial data which describes location (where)
Attribute data which specifies characteristics at that location
(what, how much, and when).
by grouping into layers based on similar characteristics (e.g.
hydrograph, elevation, water lines, sewer lines, grocery sales) and
using either:
vector data model (coverage in ARC/INFO, shape file in Arc
View)
raster data model (GRID or Image in ARC/INFO & Arc View)
17. SPATIAL DATA TYPES
continuous: elevation, rainfall, ocean salinity
areas:
unbounded: landuse, market areas, soils, rock
type
bounded: city/county/state boundaries,
ownership parcels, zoning
moving: air masses, animal herds, schools of fish
networks: roads, transmission lines, streams
points:
fixed: wells, street lamps, addresses
moving: cars, fish, deer
18. ATTRIBUTE DATA TYPES
Categorical (name):
nominal
no inherent ordering
land use types, county names
ordinal
inherent order
road class; stream class
often coded to numbers eg SSN but can’t do arithmetic
Numerical
Known difference between values
interval
No natural zero
can’t say ‘twice as much’
temperature (Celsius or Fahrenheit)
ratio
natural zero
ratios make sense (e.g. twice as much)
income, age, rainfall
may be expressed as integer [whole number] or floating point [decimal
fraction]
19. ATTRIBUTE DATA TYPES
Attribute data tables can contain locational information, such as
addresses or a list of X,Y coordinates. ArcView refers to these as
event tables. However, these must be converted to true spatial data
(shape file), for example by geocoding, before they can be
displayed as a map.
Data Base Management Systems (DBMS)
The key field is an attribute whose values uniquely identify each row
Tables are related, or joined, using a common record identifier (column
variable), present in both tables, called a secondary (or foreign) key, which may
or may not be the same as the key field.
20. RASTER DATA MODEL & RASTER DATA MODEL:
o Vector data model: Vector data models are useful for storing data that
has discrete boundaries, such as country borders, land parcels, and
streets.
best for features with discrete boundaries
property lines
political boundaries
transportation
o raster data model: [data models] A representation of the world
as a surface divided into a regular grid of cells.
attribute is represented as a single value for that cell
best for continuous features:
elevation
temperature
soil type
land use
24. DIGITAL ELEVATION MODEL
. A Digital Elevation Model (DEM) is a
specialized database that represents
the relief of a surface between points
of known elevation. By interpolating
known elevation data from sources
such as ground surveys and
photogrammetric data capture, a
rectangular digital elevation
model grid can be created
DEM is frequently used to refer to any
digital representation of a topographic
surface
A surface grid considers each sample
as a square cell with a constant
surface value.
Advantages
• Simple conceptual model
• Data cheap to obtain
• Easy to relate to other raster data
• Irregularly spaced set of points
can be converted to regular
spacing by interpolation
Disadvantages
• Does not conform to variability
of the terrain
• Linear features not well
represented
25. TRIANGULATED IRREGULAR NETWORK
TIN is a vector-based
representation of the physical land
surface or sea bottom. The basic
unit is a triangle. Used for surface
modeling.
Advantages
Can capture significant
slope features (ridges, etc)
Efficient since require few
triangles in flat areas
Easy for certain analyses:
slope, aspect, volume
Disadvantages
Analysis involving
comparison with other
layers difficult
26. APPLICATIONS AND USES OF GIS
1.GIS in Mapping:
2. Telecom and Network services:
3. Accident Analysis and Hot Spot Analysis:
4. Urban Planning:
5. Transportation Planning:
6. Environmental Impact Analysis:
7. Agricultural Applications:
8. Disaster Management and Mitigation:
27. APPLICATIONS AND USES OF GIS
9. Landslide Hazard Zonation using GIS:
10. Determine land use/land cover
changes:
11. Navigation (routing and scheduling)
12. Flood damage estimation:
13. Natural Resources Management:
14. GIS Solutions in Banking Sector:
15. Soil Mapping :
16. Land Information System:
28. APPLICATIONS AND USES OF GIS
17. Surveying:
18. Wetland Mapping:
19. GIS Applications in Geology:
20. Tourism Information System:
21. Irrigation water management:
22. Worldwide Earthquake Information System:
23. Forest Fire Hazard Zone Mapping:
24. Deforestation:
25. GIS for Business:
26. Location Identification:
29. GEO –REFERENCING
Geo-referencing means to associate
something with locations in physical space.
The term is commonly used in the
geographic information systems field to
describe the process of associating a
physical map or raster image of a map with
spatial locations.
30. IN GENERAL, THERE ARE FOUR STEPS TO
GEOREFERENCE YOUR DATA:
Add the raster dataset that you want to align
with your projected data.
Use the Georeference tab to create control
points, to connect your raster to known
positions in the map
Review the control points and the errors
Save the georeferencing result, when you
are satisfied with the alignment.
31. NEED
Georeferencing is crucial to making aerial and satellite imagery, usually
raster images, useful for mapping as it explains how other data, such as
the above GPSpoints, relate to the imagery.
Very essential information may be contained in data or images that were
produced at a different point of time. It may be desired either to combine
or compare this data with that currently available. The latter can be used
to analyze the changes in the features under study over a period of time.
Different maps may use different projection systems. Georeferencing
tools contain methods to combine and overlay these maps with
minimum distortion.
Using georeferencing methods, data obtained from surveying tools
like total stations may be given a point of reference from topographic
maps already available.
It may be required to establish the relationship between
social survey results which have been coded with postal codes or street
addresses and other geographic areas such as census zones or other
areas used in public administration or service planning.
