1. Define spatial and attributes
1. Spatial data
Spatial data describes the absolute andrelative location of geographic features.
Attribute data describes characteristicsof the spatial features. These characteristics canbe
quantitative and/or qualitative in nature, Attribute data is often referred to as tabular data.
2. Difference between a vector and raster and their advantages and disadvantages
A raster image- is made of up pixels, each a different colour, arranged to display an image.
A vector image- is made up of paths; each with a mathematical formula (vector) that tells the path
how it is shaped and what colour it is bordered with or filled by.
Advantages and disadvantages of vector and raster
Advantages of vector
Data can be represented at its original resolution and form without generalization.
Graphic output is usually more aesthetically pleasing (traditional cartographic
Since most data, e.g. hard copy maps, is in vector form no data conversion is required.
Accurate geographic location of data is maintained.
Allows for efficient encoding of topology, and as a result more efficient operations that
require topological information, e.g. proximity, network analysis.
Disadvantages of vector
The location of each vertex needs to be stored explicitly.
For effective analysis, vector data must be converted into a topological structure. This is
often processing intensive and usually requires extensive data cleaning. As well, topology is
static, and any updating or editing of the vector data requires re-building of the topology.
Algorithms for manipulative and analysis functions are complex and may be processing
intensive. Often, this inherently limits the functionality for large data sets, e.g. a large
number of features.
Continuous data, such as elevation data, is not effectively represented in vector form.
Usually substantial data generalization or interpolation is required for these data layers.
Spatial analysis and filtering within polygons is impossible
Advantages of raster
The geographic location of each cell is implied by its position in the cell matrix. Accordingly,
other than an origin point, e.g. bottom left corner, no geographic coordinates are stored.
Due to the nature of the data storage technique data analysis is usually easy to program
and quick to perform.
The inherent nature of raster maps, e.g. one attribute maps, is ideally suited for
mathematical modelling and quantitative analysis.
Discrete data, e.g. forestry stands, is accommodated equally well as continuous data, e.g.
elevation data, and facilitates the integrating of the two data types.
Grid-cell systems are very compatible with raster-based output devices, e.g. electrostatic
plotters, graphic terminals.
Disadvantages of raster
The cell size determines the resolution at which the data is represented.
It is especially difficult to adequately represent linear features depending on the cell
resolution. Accordingly, network linkages are difficult to establish.
Processing of associated attribute data may be cumbersome if large amounts of data exist.
Raster maps inherently reflect only one attribute or characteristic for an area.
Since most input data is in vector form, data must undergo vector-to-raster conversion.
Besides increased processing requirements this may introduce data integrity concerns due
to generalization and choice of inappropriate cell size.
Most output maps from grid-cell systems do not conform to high-quality cartographic
2 Different spatial data objects in GIS environment
*Points represent anything that can be described as a discrete x, y location
*Lines represent anything having a length
*Areas, or polygons, describe anything having boundaries
These data types comprise the vector model, which is the model you will deal with most often
Vector data model:
Discrete features, such as customer locations, are usually represented using the vector model.
Features can be discrete locations or events, lines, or areas. Lines, such as streams or roads, are
represented as a series of coordinate pairs. Areas are defined by borders, and are represented
by closed polygons. When you analyze vector data, much of your analysis involves working with
(summarizing) the attributes in the layer's data table.
Raster data model:
Continuous numeric values, such as elevation, and continuous categories, such as vegetation
types, are represented using the raster model. The raster data model represents features as a
matrix/lattice of cells in continuous space. A point is one cell, a line is a continuous row of cells,
and an area is represented as continuous touching cells.
Tabular data Contain information describing a map feature in the form of a table or spread
sheet. For example, a GIS database of customer locations may be linked to address and
personnel information. GIS links this tabular data to associated spatial data. The major
difference is that raster image pixels do not retain their appearance as size increases – when
you blow a photograph up, it becomes blurry for this reason. Vector images do retain
appearance regardless of size, since the mathematical formulas dictate how the image is
A microclimate is a local atmospheric zone where the climate differs from the surrounding
area. The term may refer to areas as small as a few square feet (for example a garden bed) or
as large as many square miles (for example a valley). Microclimates exist, for example, near
bodies of water which may cool the local atmosphere, or in heavily urban areas where brick,
concrete, and asphalt absorb the sun's energy, heat up, and reradiate that heat to the ambient
air: the resulting urban heat island is a kind of microclimate.
Another contributing factor to microclimate is the slope or aspect of an area. South-facing
slopes in the Northern Hemisphere and north-facing slopes in the Southern Hemisphere are
exposed to more direct sunlight than opposite slopes and are therefore warmer for longer.
The area in a developed industrial park may vary greatly from a wooded park nearby, as natural
flora in parks absorb light and heat in leaves, that a building roof or parking lot just radiates
back into the air. Advocates of solar energy argue that widespread use of solar collection can
mitigate overheating of urban environments by absorbing sunlight and putting it to work
instead of heating the foreign surface objects.
A microclimate can offer an opportunity as a small growing region for crops that cannot thrive
in the broader area; this concept is often used in permaculture practiced in northern temperate
climates. Microclimates can be used to the advantage of gardeners who carefully choose and
position their plants. Cities often raise the average temperature by zoning, and a sheltered
position can reduce the severity of winter. Roof gardening, however, exposes plants to more
extreme temperatures in both summer and winter.
Tall buildings create their own microclimate, both by overshadowing large areas and by
channelling strong winds to ground level. Wind effects around tall buildings are assessed as
part of a microclimate study.
Microclimates can also refer to purpose made environments, such as those in a room or other
enclosure. Microclimates are commonly created and carefully maintained in museum display
and storage environments. This can be done using passive methods, such as silica gel, or with
active microclimate control devices
Disadvantages for GIS use in the government
There are some disadvantages to using GIS in a government setting. Possible concerns include
the idea that GIS decreases the democratic right of the people or that the technology is taking
power away from the masses and into the hands of a few because only a limited number of
people know how to use the technology. This is true to some extent. First, costs for GIS
and powerful computers to operate it are decreasing; however the costs of producing high-
data are increasing . Companies who produce data can charge high prices, and the cost of
hiring staff to generate data on site can be expensive as well. Therefore, many cities or small
local governments could afford the computers and necessary software but creating the data
suitable to their individual needs may be out of reach. The costs of using GIS once the data
been collected and created are minimal; however, the initial building phase involves a
investment from the agency .
A data input subsystem allows the user to capture, collect, and transform spatial and thematic data
into digital form. The data inputs are usually derived from a combination of hard copy maps, aerial
photographs, remotely sensed images, reports, survey documents, etc.
Data Storage and Retrieval
The data storage and retrieval subsystem organizes the data, spatial and attribute, in a form which
permits it to be quickly retrieved by the user for analysis, and permits rapid and accurate updates to
be made to the database. This component usually involves use of a database management system
(DBMS) for maintaining attribute data. Spatial data is usually encoded and maintained in a
proprietary file format.
Data Manipulation and Analysis
The data manipulation and analysis subsystem allows the user to define and execute spatial and
attribute procedures to generate derived information. This subsystem is commonly thought of as the
heart of a GIS, and usually distinguishes it from other database information systems and computer-
aided drafting (CAD) systems.
The data output subsystem allows the user to generate graphic displays, normally maps, and tabular
reports representing derived information products.
The critical function for a GIS is, by design, the analysis of spatial data.
Education is a field where integration of
multimedia and GIS can bring enormous
benefits. Students will learn faster and more
efficiently. In addition, it will be possible to
individualize learning and tune it to particular
preferences of each student. In this model a
teacher becomes a guide rather than a repository
of facts. It is the computer that takes on a role of
"an infinitely patient teacher."
GIS can use and combine all layers that
are available for an area, in order to produce an
overlay that can be analyzed by using the same
GIS. Such overlays and their analysis radically
change decision-making process that include,
• Site selection
• Simulation of environmental effects (for
example, creating perspective views of
a terrain before and after mining)
• Emergency response planning (for
example, combining road network and
earth science information to analyze the
effects of a potential earthquake)
5.3 Land Information
GIS has aided management of land
information by enabling easy creation and
maintenance of data for land records, land
planning and land use. GIS makes input, updates,
and retrieval of data such as tax records, land-use
plan, and zoning codes much easier then during
the paper-map era. Typical uses of GIS in land
information management include managing land
registry for recording titles to land holdings,
preparing land-use plan and zoning maps,
cadastral mapping etc. Input of data into a land
information GIS includes: politicaladministrative boundaries, transportation, and
The environmental field has long used
GIS for a variety of applications that range from
simple inventory and query, to map analysis and
overlay, to complex spatial decision-making
systems. Examples include: forest modeling,
air/water quality modeling and monitoring,
environmentally sensitive zone mapping,
analysis of interaction between economic,
meteorological, and hydrological & geological
change. Typical data input into an environmental
GIS include: elevation, forest cover, soil quality
and hydrogeology coverage.
Archaeology, as a spatial discipline, has
used GIS in a variety of ways. At the simplest
level, GIS has found applications as database
management for archaeological records, with the
added benefit of being able to create instant
maps. It has been implemented in cultural
resource management contexts, where
archaeological site locations are predicted using
statistical models based on previously identified
site locations. It has also been used to simulate
diachronic changes in past landscapes, and as a
tool in intra-site analysis
5.7 Natural Hazards
Areas vulnerable to earthquakes, floods,
cyclones, storms, drought, fire, volcano, land
slides, soil erosion can be used to accurately
predict future disasters.
GIS has been emerging as a strong tool
for many areas of forestry, from harvesting
schedules to urban forestry.
5.9 Military GIS
GIS offers a virtually unique ability to
aggregate, automate, integrate and analyze
geographical data, which further enhance the
intelligence base for defense operations
GIS enables study of sea level change,
marine population, sea surface temperature, and
coral reef ecosystem
5.11 Water Resources
GIS enables spatial representation of
ground water resources, waste quality, watershed
management, surface water management, and
5.12 GIS in agriculture and soil
Data includes information on the
country’s land resources including physiography,
soils, climate, hydrology, cropping systems and
6 Currently available GIS software
Some of the big players providing GIS
• ESRI’s ArcGIS: ArcGIS is a scalable
system for geographic data creation,
management, integration, analysis, and
• Autodesk’s AutoCAD Map: This
software is for precision mapping and
geographic information system (GIS)
analysis in the AutoCAD environment.
It has the special tools needed to create
and produce maps and geographic
information—plus all the underlying
functionality of AutoCAD.
• Autodesk’s GIS design overlay:
Autodesk GIS design overlay combines
powerful server technology with the
mapping and design capabilities of
AutoCAD Map®, enabling access to
enterprise geographic and design data
via desktop, web, and mobile client
• Intergraph’s GeoMedia