A geographic information system (GIS) is a system designed to capture,
store, manipulate, analyze, manage, and present all types of geographical
data. The key word to this technology is Geography – this means that
some portion of the data is spatial. In other words, data that is in some way
referenced to locations on the earth.
Coupled with this data is usually tabular data known as attribute
data. Attribute data can be generally defined as additional information
about each of the spatial features.
It is the partnership of these two data types that enables GIS to be such an
effective problem solving tool through spatial analysis.
GIS is more than just software. People and methods are combined with
geospatial software and tools, to enable spatial analysis, management large
datasets, and the display of information in a map/graphical form.
What can we do with GIS ??
GIS can be used as tool in both problem solving and
decision making processes, as well as for visualization
of data in a spatial environment.
Spatial data, also known as geospatial data, is information about a
physical object that can be represented by numerical values in a
geographic coordinate system. Geospatial data can be analyzed to
(1) the location of features and relationships to other features
(2) where the most and/or least of some feature exists
(3) the density of features in a given space
(4) what is happening inside an area of interest (AOI)
(5) what is happening nearby some feature or phenomenon
(6) and how a specific area has changed over time (and in what
We can map the spatial location of real-world features and
visualize the spatial relationships among them.
Example: below we see a map of agricultural districts (in green)
layered over soil types. We can see visual patterns in the data by
determining what soil types are best suited for ag districts.
We can map quantities, such as where the most and least are, to
find places that meet their criteria or to see the relationships
Example: below is a map of cemetery locations . The map shows
the cemetery locations as dots (dot density) and each county is
color coded to show where the most and least are (lighter blue
means fewer cemeteries).
Sometimes it is more important to map concentrations, or a
quantity normalized by area or total number. Example: Below
we have mapped the population density of an area.
We can use GIS to determine what is happening or what features are
located inside a specific area/region. We can determine the
characteristics of "inside" by creating specific criteria to define an area
of interest (AOI).
Example: below is a map showing noise 'pollution' near an airport in a
city. If we add demographic data from the Census to this map we can
determine the socioeconomic characteristics of people that live within
the defined 'noise pollution' area of interest.
We can find out what is happening within a set distance of a
feature or event by mapping what is nearby using geo processing
tools like BUFFER. Example: below we see the effects on
features within specified radii of a simulated explosion. Use of
buffering tools to generate set distances can aid in emergency
response to disasters like these.
We can map the change in a specific geographic area to
anticipate future conditions, decide on a course of action, or to
evaluate the results of an action or policy. Example: below we
see land use maps of an area showing changes in residential
development from 1951 to 1999. The dark green shows forest,
while bright yellow shows residential development.
• Involves surveys, review of exiting infrastructure.
• GIS- integrates, manage, analyze and visualize the wide range of
• GIS- data management tools to manage and share data between
GIS and CAD soln.
• Detailed understanding of the location of assets for transport
• Up to date information systems for travellers.
• The wide choice of travel options require true multi-modal
Watershed management is a term used to describe the
process of implementing land use practices and
water management practices to protect and improve the
quality of the water and other natural resources within
a watershed by managing the use of those land and water
resources in a comprehensive manner.
GIS map water resources and link them to a database
Data – land use & land cover, geology, soils, hydrography &
Planners/Engineers link their modelling system to the
FLOOD CONTROL –
Determine flood zones.
Estimate the magnitude of high-flow events, the probability of
low flow events.
Identify high-potential erosion areas.
Derive physical characteristics area, perimeter, soil data etc.
Plot the flood hazard zoning map.
Plot the food shelter suitability map.
Zoning , subdivision planning
Urban land use mapping
Housing renovation programs
Encroaching urban problems of even small
GPS or Global Positioning System is a network of orbiting
satellites that send precise details of their position in space back to
earth. The signals are obtained by GPS receivers, such as
navigation devices and are used to calculate the exact position,
speed and time at the vehicles location. The very first GPS system
was developed in the 1960’s to allow ships in the US Navy to
navigate the oceans more accurately.
There are three parts to a GPS system: a constellation of
between 24 and 32 solar-powered satellites ( including three
backup satellites ) orbiting the earth in orbits at an altitude of
approximately 20000 kilometers, a master control station and
four control and monitoring stations and GPS receivers such as
the one in a car.
Each of the satellites is in an orbit that allows a receiver to detect
at least four of the operational satellites. The satellites send out
microwave signals to a receiver where the built-in computer uses
these signals to work out your precise distance from each of the
four satellites and then triangulates your exact position on the
planet to the nearest few meters based on these distances.
SURVEYING-Many companies in India and abroad uses GPS
to locate different points, preparing contour maps, giving
alignments of roads, bridges where precision is very essential.
This system gives us the accurate geographic position required
for land surveying.
NAVIGATION-It is used for navigation purposes in aircraft,
ships, submarines etc.
MILITARY-It is now exceedingly used to locate the enemy
targets and subsequently hitting them by GPS information
PUBLIC USES-For public use simpler version are available for
locating the vehicles, the individuals and the places, in hiking
and mountaineering expeditions and other number of
It helps to survey with many times greater Precision.
This system is fast replacing with conventional methods of
surveying like Triangulation, Traversing, etc.
It helps to complete a Survey with lesser time and thus helps
to cut down the Completion Period.
It Reduces the Difficulty of taking manual measurements to
With GPS there is a very less chances of error. And this
error may come only due to the instrument malfunction.