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PRACTICAL 4- SPATIAL INFORMATION TECHNOLOGY
SPATIAL INFORMATION TECHNOLOGY
The word spatial is derived from space. It refers to the features and the phenomena distributed
over a geographically definable space having physically measurable dimensions.
The spatial information technology relates to the use of the technological inputs in collecting,
storing, retrieving, displaying, manipulating, managing and analysing the spatial information.
GEOGRAPHIC INFOMATION SYSTEM
A system for capturing , storing, checking, integrating, manipulating, analysing and displaying data
which are spatially referenced to the earth.
Forms of geographical information
Two types of the data represent the geographical information. These are spatial and non spatial
data.
Spatial data
Spatial data are characterised by their positional, linear and areal forms of appearances.
The most common source of spatial data is topographical or thematic maps in hard copy [paper]
or soft copy [digital]
Non spatial data
The data those describe the spatial data are called as non spatial or attribute data.
Advantages of GIS over manual methods
Users can interrogate displayed spatial features and retrieve associated attribute
information for analysis
Maps can be drawn by querying or analysing attribute data
Spatial operations[overlay, buffering] can be applied on integrated database to generate
new sets of information
Different items of attribute data can be associated with one another through shared
location code.
COMPONENTS OF GIS
The important components of GIS include
1. Hardware
2. Software
3. Data
4. People
5. Procedures
Hardware
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Hardware comprises of the processing storage, display and input and output sub systems.
Software
An application software with the following functional modules is important pre requisite of a GIS
Software related to data entry, editing and maintenance
Software related to analysis/ transformation/manipulation
Software related to data display and output.
Data
Spatial data and related tabular data are the backbone of GIS. The existing data may be acquired
from a supplier or a new data may be created/collected. The digital map forms the basic data
input for GIS. Tabular data related to the map objects can also be attaché to the digital data. A GIS
will integrate spatial data with other data resources.
People
GIS users have a very wide range from hardware and software engineers to resources and
environmental scientists, policy makers, and the monitoring and implementing agencies. These
people use GIS to evolve a decision support system and solve real time problems.
Procedures
It include how the data will be retrieved, input into the system, managed, transformed, analysed
and finally presented in a final output.
Spatial data formats
The spatial data is represented in two formats
1. Raster
2. Vector
Raster data format
Raster data represent a graphic feature as a pattern of grids of squares.
The raster file formats are Used for the following activities
For digital representation of aerial photographs, satellite images, scammed paper maps
and other applications with very detailed images
When costs need to kept down
When the map does not require analysis of individual map features
When backdrop maps are required
Vector data format
In vector data each point is expressed as two or three numbers referred to as X, Y and Z.
The vector files are Used for
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Highly precise applications
When file size are important
When individual map features require analysis
When descriptive information must be stored
Sequence of GIS activities
The following sequence of the activities are involved in GIS related work
1. Spatial data input
2. Entering of the attribute data
3. Data verification and editing
4. Spatial and attribute data linkages
5. Spatial analysis
Spatial data input
Spatial data input can be done in 2 ways
Acquiring digital data sets from a data supplies
Creating digital data sets by manual input
The most common ways of putting data into a GIS are through
Digitisers
scanners
Entering of the attribute data
Attribute data define the properties of a spatial entry that need to be handled in the GIS but
which are not spatial.
Data verification and editing
The spatial data captured into a GIS require verification for the error identification and
corrections so as to ensure the data accuracy.
Spatial and attribute data linkages
The spatial data is linked to the attribute data.
Spatial analysis
The analysis functions use the spatial and non spatial attributes in the data base to answer
questions about the real world. The objective of geographic analysis is to transform data
into useful information to satisfy the requirements of the decision makers.
The following spatial analysis operation may be undertaken using GIS
a. Overlay
b. Buffer analysis
c. Network analysis
d. Digital terrain model
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Overlay
GIS makes it possible to overlay two or more thematic maps of the same area to obtain a new
map layer.
Use – to study the changes in land use
Buffer operation [proximity analysis]
A buffer of a certain specified distance can be created along any point, line or area feature.
Buffer operation will generate polygon feature types irrespective of geographic features and
delineates spatial proximity.
Use- to locate the areas/population benefitted or denied of the facilities and services
