GIS

Geographic Information System (GIS)
A geographic information system (GIS) is a
computer based tool for mapping and analyzing
things that exist and events that happen on earth.
GIS technology integrates common database
operation such as query and statistical analysis
with the unique visualization and geographic
analysis benefits offered by maps.
These abilities distinguish GIS from other
information systems and make it valuable to a
wide range of public and private enterprises for
explaining events, predicating outcomes, and
planning strategies. How does it (GIS) work?
GIS stores information about the world as a
collection of thematic layers that can be linked
together by geography. This simple
but extermly powerful and versatile concept has
proven invaluable for solving many real-world
problems from tracking delivery vehicles, to
recording details of planning applications, to
modeling global atmospheric circulation.
Geographic References:
Geographic information contains either an explicit
geographic reference, such as a latitude and
longitude or national grid coordinate, or an implicit
reference such as an address, postal code, census
tract name, forest stand identifier, or road name.
An automated process called geocoding is used to
create explicit geographic references from implicit
references. These geographic references allow you
to locate features, such as a business or forest
stand, and events, such as an earthquake, on the
earth's surface for analysis.
Vector and Raster Model:
GIS work with two fundamentally different types of
geographic models: the 'vector' model and 'raster'
model. In the vector model, information about
points, lines, and polygons is encoded and stored
as a X,Y coordinate. Linear features, such as
roads and rivers, can be stored as a collection of
point coordinates. Polygonal features, such as
sales territories and rivers catchments, can be
stored as closed loop of coordinates.
The vector model is extremely useful for describing
discrete features, but less useful for describing
continuously varying features such as soil type or
accessibility costs for hospitals. The raster model
has evolved to model such continuous features. A
raster image comprises a collection of grid cells
rather like a scanned map or pictures. Both are
vector and raster models for storing geographic
data have unique advantages and disadvantages.
Modern GISs are able to handle both models.
Components of GIS:
Hardware: Hardware is the computer on
which a GIS operates. Today, GIS
software runs on wide range of hardware
types, from centralized computer servers
to desktop computers used in stand-aline
or networked configurations.
Software: GIS software provides the
functions and tools needed to store,
analyze, and display geographic
information. Software components are
given below:
1. Tools for the input and manipulation of
geographic information
2. a database management system (DBMS)
3. tools that support geographic query, analysis,
and visualization
4. a graphical user interface for easy access to
tools.
component of GIS is the data. Geographic
data and related tabular data can be
collected in house or purchased from a
commercial data provider. A GIS will
integrate spatial data with other data
resources and can even use a DBMS,
used by most of organizations to
recognize and maintain their data, to
manage spatial data.
without the people who manage the
system and develop plans for applying it
to real world problems. GIS users range
from technical specialists who design
and maintain the system to those who
use it to help them perform their
everyday work.
according to a well designed plan and
business rules, which are the models and
operating practices unique to each
organization.