to GIS

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Introduction to GIS
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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
operations 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, predicting outcomes, and planning
strategies. (Environmental Systems Research
Institute, ESRI)
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What distinguishes GIS from other forms of
information systems, such as databases and
spreadsheets, is that GIS deals with spatial
information.
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GIS has the capability to relate layers of data
for the same points in space, combining,
analyzing and, mapping out the results.
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Spatial information uses location, within a
coordinate system, as its reference base. The
most common representation of spatial information
is a map on which the location of any point could
be given using latitude and longitude, or local
grid references such as the National Grid.
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A Geographic Information System allows one
to Portray features located on the earths
surface, as you would find on traditional paper
maps. Locate features on a map using
coordinates Provide descriptions of
features Perform queries and analysis of spatial
data Store, manage, update and retrieve data in
an organized, efficient manner
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Components of a GIS A working GIS is made up of
five key components Hardware the computer on
which the GIS operates. It used to be a
mainframe, desktop computers, laptops, and now
hand held units. Software the software that
provides the functionality and tools needed to
store, analyze, and display geographic
information. Key software components are a.
Tools for the input and manipulation of
geographic information b. Database management
system c. Tools that support geographic query,
analysis, and visualization d. A graphical
interface (GUI) for easy access to tools
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Components of a GIS Data possibly the most
important component of all and can be the most
difficult to obtain. Geographic data and related
tabular data can be collected in-house, from
local (AGRC) or federal (USGS) agencies or
purchased from a commercial provider. People
GIS is of limited value without the people who
manage the system and develop plans for applying
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. Methods A successful GIS
operates according to a well designed plan and
business rules, which are the models and
operating practices unique to each organization.
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The Software ArcGIS ArcGIS is an
integrated GIS consisting of three
key parts ArcGIS the desktop software ArcSDE
the interface for managing databases
(SDE Spatial Database Engine) ArcIMS
software, internet-based GIS for the
distribution of GIS data and services
(Internet Map Server)
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GIS data are usually stored in more than one
layer in order to overcome the technical
problems caused by handling very large amounts
of information at one time. It is easier to work
with complex spatial problems one layer at a
time, to enable the revision of the data without
having to overhaul the entire information system.
This is a fundamental aspect of GIS, and working
with layers of geographical information is known
as data integration.
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Geospatial Data

• Attribute Data
• Spatial Data

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Attribute Data
Attributes are numeric or alphanumeric data that
describe features of points, lines, or areas
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Spatial Data
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The GIS data points, polylines, and polygons
saved in separate layers, but displayed together
with unique attributes.
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Spatial Data
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Vector and Raster Conversions
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Data Manipulation GIS Analysis
Geographic information systems perform
six processes Input Manipulation Management Quer
y Analysis Visualization
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Recode Operations
Results in a new layer by reclassing the value of
an input cell to that of a new value
Current Vegetation
Cross- reference
Fire Fuels
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Overlay Operations
Results in a new layer by associating the values
from two or more data layers
GIS Analysis Linear miles of stream and road
classes by rangeland vegetation classes
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Linear Operations
Results in a new layer whose output values are a
function of distance or connectivity
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Area Operations
Results in a new layer whose values are a
function of some area measurement
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Generate Maps and Reports
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What kind of data do I need for a GIS and where
do I obtain it .
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• Agriculture Land Use
• Management
• Forestry Wildlife Management
• Archaeologists
• Geologists
• Municipal Facilities Management
• Hydrologists

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• Forest plan revisions
• Transportation planning
• Assessment for building plans
• Public meetings and court cases

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