Transcript Document

Definition: GIS is a System of computer software,
hardware and data, and personnel to help
manipulate, analyze and present information that is
tied to a spatial location –
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spatial location – usually a geographic location
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information – visualization of analysis of data
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system – linking software, hardware, data
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personnel – the most critical key to the successful use of
a GIS
http://www.gis.com/
Types of data that can be included in a GIS
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Cadastral information
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Images
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Land Uses
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Inventory of Natural Resources
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Market Analysis and Trends
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Planning Schemes
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Risk Analyses
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Analytical Models and Simulations
In summary if the information has any spatial component it
can be presented within a GIS.
History of GIS
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1960s – Restricted to paper-based systems “Maps”
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1970s – First Digital Mapping
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Early 1980s – first Computer Aided Design or CAD packages
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Mid 1980s – First GIS using Workstations
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Late 1980s – Desktop Mapping, Integration of CAD with
Databases, birth of PC-based systems
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Early 1990s – Desktop GIS with full integration of data
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Mid 1990s – GIS became more accessible with Windows based
destop GIS
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Late 1990s – GIS became functional over the Internet
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Early 2000s – full integration of GIS into applications e.g. In
Vehicle Navigation Systems
How does GIS vary from other Graphics
Programs ?
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Computer-aid design (CAD), computer cartography,
database management and remote-sensing were all
important in the development of GIS, however,
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AA GIS allows information to be linked to an object, such
as point, line or polygons. Consequently information can
be calculated from the topography of the object or
information can be attached to the object and stored in a
separate table.
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A GIS has the ability to shade various land parcels
(districts) according to ranges of specified variables. This
makes identification of spatial relations within the data set
easy to identify.
DIFFERENCE BETWEEN A GIS AND
MAPS/ATLASES
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Maps have to be printed and in relatively large formats
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Although maps can be compiled into an Atlas, they are not
seamless and you have to compare one page with another
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Maps have to be printed at fixed scales
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Maps cannot provide all the annotation you might require
with respect to shading and place names
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Although Maps should always include a scale bar it is still
not easy to calculate the lengths of features represented
on the map and is almost impossible to determine areas
with any reasonable accuracy.
GIS Maps are Customizable
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With a GIS you can combine information that you wish to use
and ignore information that is redundant to your needs
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Each feature of a Map is stored in a GIS as a series of files that
collectively are referred to as a “layer” or “coverage”. You can
add different coverages onto each other
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A GIS allows the different representation and colour of points,
the colour and style of lines, the colour and shading properties
of polygons, the colour, font, size and orientation of labels to be
changed
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One of the most important aspects of a GIS is the displaying of
information attached to the coverage which can also be
represent by colour gradients or by unique colours according to
attributes with a linked table of information
GIS Maps are Searchable
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Any of the data whether it be within the associated table or
be a measurement of the object and whether it’s numerical
or text can be searched and identified.
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Searches can be simple such as find all estuaries which
are always open to compound searches such as find all
estuaries that are always open and have a mangrove
population.
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Searches can be based on features based on the
parameters of map features - e.g. the length of sandy
beaches along a coastline that are longer than 5km
GIS Maps are Updatable
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Since the information is stored electronically information is
easily updated without require republishing.
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This information ca be writen to CD and can dispatched to
offices or made available via a network
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More recently advance in GIS applications allow
information to be updated and available to the entire users
of the World Wide Web.
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Consequently information can be maintained in its most
current form and optimizes decision-making.
What Computers Would You Need To Run A
GIS?
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A typical GIS is fairly complex and the databases and
images are usually large - they consequently take up
considerable disk space.
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Needing to handle so much data requires a fair amount of
memory and processing power.
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Backups of data can be undertaken using tapes or rewritable CDs
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Often GIS software is graded into being able to view data,
to minor alterations, to full customizing and programming
(usually BASIC) and finally through to a full centrally
managing large or “corporate” application.
Getting Maps and Data into a GIS
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Geocoding one Table against an already existing GIS
table and feature list
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Using a Digitizing Board
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Scan a pre-existing map and then geo-reference it
within the GIS
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Using a GPS to field map features
Where Can You Get Data?
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Purchase data from government and commercial vendors.
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Data supplied via internet services, or via online viewing
and downloading of files, e.g. Western Cape Nature
Conservation Board is starting this.
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Meta databases – which can be maps which provide
information on suppliers of spatial information.
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With high bandwidths you can even log into different
servers and mix data from different sources, and first
system now exists where you can can upload your data to
a map service for distribution via the world-wide web.
Who Produces Digital Maps?
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North America - USGS provide togographical maps, satellite
imagery, correct orthophotos, scanned copies of paper maps,
etc.
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South Africa – Chief Directorate Surveys and Mapping provide
the above products and charge only the cost of CD cutting.
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Increasingly in South Africa, private companies are providing
more of the data. Consequently Computamaps in Cape Town
has developed and markets very high resolution (20m) Digital
Terrain Model for SouthAfrica that are extensively used in the
mobile telecommunications industry. The Knowledge Factor
has map of all land parcels in South Africa and records of
ownership as reflected in the Deeds Office.
Obtaining New Data
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The USGS develops from aerial photography, digital, geocorrected orthophotographs of pan imagery at 1 metre
resolution for the entire country every 5 years.
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In South Africa many parts have never had any
orthophotographs prepared. The most accurate digital elevation
model which records height data was for a resolution of 200
metre raster grid cells from the Surveyor General for South
Africa.
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More Accurate Digital Terrain Information can be acquired using
the LIDAR (look this up) and Digital Elevation Models with
centimeter resolution for small areas are being prepared.
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Virtually all new maps being prepared nowadays are done
through a GIS and hand drawing is very much a thing of the
past.
Types Of GIS
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There are two types of GIS which store the information in
very different format. These are known as vector-based
and raster-based.
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Originally there was little cross functionality between the
two systems, however, most current software has the
ability to present both systems
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Some software such as TNT Mips has extensive
functionality in both systems.
Raster: Grids
Uses “pixels” for
location and value
attributes and includes
satellite-images and
digital aerial photos are
already in this format.
Each grid will have a value that corresponds to some
feature, for example water might have a value of 6 and
there fore all grids which have a value of 6 represents
water. Raster-based GIS systems are not strong on the
data-base functionality, but are good for spatial
analysis, modeling and visualizations.
Vector – Linear: Points, Lines & Polygons
Vector GIS use points, lines and
polygons to represent features.
Since such features are precisely
define by geographical coordinates, they are useful for
accurate calculation of
measurements and are easily
attached to tabulated data for
querying.
Vector-based GIS are used
extensively for management
such as municipal offices would
require
Application of GIS to Pollution Management
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For pollution control you will normally use
Environmental Sensitivity Index Maps developed by
NOAA. These are used by coastal managers for all
forms of oil/chemical pollution and contain three
types of information, namely:-
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Coastline Information
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Sensitive Biological Resources
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Human Use Features
Thematic Mapping - for Sensitivity Atlases
Coastline Information that is colour coded with
respect to either type of coastal and/or its
vulnerability to pollution which ranges from
Exposed Rocky Headlands which are the least
vulnerable and will be coloured with cold colours
such blue/green to estuarine environment
(marshes and mangroves) which are the most
vulnerable to the effects of pollution and are
coloured warm colours such as red/orange.
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Intertidal
Exposed Rocky Shores
Exposed, Solid Man-Made
Structures
Exposed, Wave-Cut Platforms
Sandy Beaches
Mixed Sand and Gravel
Beaches
Gravel Beaches
Exposed Tidal Flats
Sheltered Rocky Shores and
Scarps
Sheltered, Solid Man-Made
Structures
Peat Shores
Sheltered Tidal Flats
Salt to Brackish Marshes
Mangroves Inundated
Subtidal
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Coral Reefs
Seagrasses
Kelp
Soft Bottom
Mixed Hard Bottom
On-Water
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Off shore
Bays and Estuaries
Sensitive Biological Featuresused in USA (NOAA)
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Marine: Mammal, Dolphin, Manatee, Seals, Otters, Whale,
Terrestrial Mammal: Primate, Canine, Feline,
Small Mammal: Hyrax and threatened, endangered, or
rare species.
Bird: Diving Bird, Gull/Tern, Pelagic, Raptor, Shorebird,
Wading Bird, Waterfowl
Reptile/Amphibian: Alligator/Crocodile, Turtle, other rare
species, especially aquatic/wetland concentration areas.
Fish: Diadromous, Nursery Estuarine Fish, Resident
Estuarine Fish, Freshwater Fish, Benthic Marine Fish,
Pelagic Marine Fish.
Shellfish/Insect: Bivalve, Cephalopod, Crab, Echinoderm,
Gastropod, Lobster/Crayfish, Shrimp, Insect
Habitat/Rare Plant: Coral Reef, Floating Aquatic
Vegetation, Hardbottom Reef, Kelp Bed, Rare, Submerged
Aquatic Vegetation, Worm Bed
Sensitive Human Resources
Human Use Resources that are depicted as both
shading and symbols
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Protected marine sites (reserves/sanctuaries),
Recreational sites including swimming beaches,
angling spots, mariculture sites
Commercial and subsistance gathering of marine
resources (mussels, bait, crayfish), coastal
developments such as harbours and marinas,
power plants including nuclear, mining and marine
intakes and discharges (e.g. a fish factor will take
in clean water for processing and discharge this
water with discharges of fish oil which are potential
pollutants).
Sensitive Human Resources - continued
Recreation/Access: Access - Vehicular access to the shoreline,
Beach - High-use recreational beaches, Boat Ramp, Diving Site, Highuse recreational areas, Marina, Recreational Fishing, High-use
recreational areas
Management Areas: Reservation, Marine Sanctuary, National Park,
Park - State and regional parks, Special Management Areas - Usually
water-associated,Wildlife Refuge, Preserve, Reserve
Resource Extraction Site: Aquaculture Site - Hatcheries, ponds, and
pens, Commercial Fishery, Log Storage Area, Mining Intertidal/subtidal mining leases, Subsistence - Designated harvest
sites, Water Intake - Industrial; drinking water; cooling water,
aquaculture
Cultural Resource: Archaeological Site - Water-, coastal-, or wetlandassociated, Historical Site - Water-, coastal-, or wetland-associated
All of these features are put onto maps using an ICONbased