CIVL 1101
What is GIS?
What is GIS?
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What is GIS?
 Geographical Information Systems (GIS) can be regarded as the high‐tech equivalent of the map.
Hydrology
 GIS integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically g g,
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referenced information.
Parcels Aerial Photos
Elevation
What is GIS?
What is GIS?
 An individual map contains a lot of information which is used in different ways by different individuals and organizations.  GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, y y
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and trends in the form of maps, globes, reports, and charts.
Data Analysis
Data Storage
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Data Input
What is GIS?
Data Visualization
What is GIS?
 The power of a GIS comes from the ability to relate different information in a spatial context and to reach a conclusion about this relationship.  Most of the information we have about our world contains a location reference, placing that information at some point on ,p
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the globe. CIVL 1101
What is GIS?
What is GIS?
 When rainfall information is collected, it is important to know where the rainfall is located.  This is done by using a location reference system, such as longitude and latitude, and perhaps elevation. What is GIS?
 When rainfall information is collected, it is important to know where the rainfall is located.  This is done by using a location reference system, such as longitude and latitude, and perhaps elevation. What is GIS?
 Comparing the rainfall information with other information, such as the location of marshes across the landscape, may show that certain marshes receive little rainfall. 2/9
What is GIS?
 This fact may indicate that these marshes are likely to dry up, and this inference can help us make the most appropriate decisions about how humans should interact with the marsh. What is GIS?
 A GIS, therefore, can reveal important new information that leads to better decision‐making.
What is GIS?
 Many computer databases that can be directly entered into a GIS are being produced by Federal, State, tribal, and local governments, private companies, academia, and nonprofit organizations.  Different kinds of data in map form can be entered into a GIS.
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U.S. Geological Survey (USGS) digital line graph (DLG) data of roads.
USGS DLG of rivers.
CIVL 1101
What is GIS?
What is GIS?
 Many computer databases that can be directly entered into a GIS are being produced by Federal, State, tribal, and local governments, private companies, academia, and nonprofit organizations.  Different kinds of data in map form can be entered into a GIS.
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USGS digital elevation (DEM).
USGS DLG of contour lines (hypsography).
What is GIS?
 Many computer databases that can be directly entered into a GIS are being produced by Federal, State, tribal, and local governments, private companies, academia, and nonprofit organizations.  Different kinds of data in map form can be entered into a GIS.
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What is GIS?
 A GIS can also convert existing digital information, which may not yet be in map form, into forms it can recognize and use.  For example, digital satellite images can be analyzed to produce a map of digital information about land use and land cover. Landsat 7 satellite image from which land cover
information can be derived.
What is GIS?
 A GIS can also convert existing digital information, which may not yet be in map form, into forms it can recognize and use.  Likewise, census or hydrologic tabular data can be converted to a maplike form and serve as layers of thematic information in a GIS.
Part of a census data file containing address information.
USGS scanned, rectified topographic map
USGS digital orthophoto quadrangle
What is GIS?
 Many computer databases that can be directly entered into a GIS are being produced by Federal, State, tribal, and local governments, private companies, academia, and nonprofit organizations.  Different kinds of data in map form can be entered into a GIS.
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USGS geologic map
Satellite image data has been analyzed to
indicate classes of land uses and cover.
Part of a hydrologic data report indicating the discharge
and amount of river flow recorded by a particular
streamgage that has a known location.
What is GIS?
 How can a GIS use the information in a map?  If the data to be used are not already in digital form, that is, in a form the computer can recognize, various techniques can capture the information.
CIVL 1101
What is GIS?
What is GIS?
 How can a GIS use the information in a map?
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What is GIS?
 Two‐ and three‐dimensional contour maps created from the surface modeling of sample points from pH measurements
 A GIS can be used to emphasize the spatial relationships among the objects being mapped.  While a computer
While a computer‐aided
aided mapping system may represent a road mapping system may represent a road
simply as a line, a GIS may also recognize that road as the boundary between wetland and urban development between two census statistical areas. Points with pH values of oil.
What is GIS?
 Since much of the information in a GIS comes from existing maps, a GIS uses the processing power of the computer to transform digital information, gathered from sources with different projections, to a common projection.
An elevation image from a satellite image of Minnesota
exists in a different scale and projection than the lines on
the digital file of the State and province boundaries.
Contour map made from soil pH values
What is GIS?
 GIS isn’t limited to flat maps and databases.  There are many extensions that enable things such as three‐
dimensional visualization and analysis and much more.
The elevation image has been reprojected to match the
projection and scale of the State and province boundaries.
What is GIS?
 It is impossible to collect data over every square meter of the Earth's surface. Therefore, samples must be taken at discrete locations.  A GIS can be used to depict two‐ and three‐dimensional characteristics of the Earth's surface, subsurface, and ,
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atmosphere from points where samples have been collected.
 For example, a GIS can quickly generate a map with isolines that indicate the pH of soil from test points.  Two‐ and three‐dimensional contour maps created from the surface modeling of sample points from pH measurements can be analyzed together with any other map in a GIS covering the area.
What is GIS?
 GIS isn’t limited to flat maps and databases.  There are many extensions that enable things such as three‐
dimensional visualization and analysis and much more.
CIVL 1101
What is GIS?
What is GIS?
 Have there ever been gas stations or factories that operated next to the swamp?  Were any of these uphill from and within 2 miles of the swamp?  A GIS can recognize and analyze the spatial relationships A GIS can recognize and analyze the spatial relationships
among mapped phenomena.  Conditions of adjacency (what is next to what), containment (what is enclosed by what), and proximity (how close something is to something else) can be determined with a GIS.
What is GIS?
 Sources of pollution are represented as points. The colored circles show distance from pollution sources and the wetlands are in dark green.
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What is GIS?
 A GIS can simulate the movement of materials along a network of lines.  These illustrations show the route of pollutants through a stream system. Flow directions are indicated by arrows.
What is GIS?
 Using maps of wetlands, slopes, streams, land use, and soils, the GIS might produce a new map layer or overlay that ranks the wetlands according to their relative sensitivity to damage from nutrient runoff.
Shaded-relief map and contour lines generated
from the digital elevation model in the study area.
What is GIS?
 When nutrients from farmland are running off into streams, it is important to know in which direction the streams flow and which streams empty into other streams.  This is done by using a linear network.  It allows the computer to determine how the nutrients are It allows the computer to determine how the nutrients are
transported downstream.  Additional information on water volume and speed throughout the spatial network can help the GIS determine how long it will take the nutrients to travel downstream.
Map showing the steepness of slopes in the study
area, created by GIS from the digital elevation model.
What is GIS?
 Using maps of wetlands, slopes, streams, land use, and soils, the GIS might produce a new map layer or overlay that ranks the wetlands according to their relative sensitivity to damage from nutrient runoff.
Distances to streams as measured by three 200-meter
buffers derived from a digital map of hydrography.
Map indicating various land uses in the study area.
CIVL 1101
What is GIS?
What is GIS?
 Using maps of wetlands, slopes, streams, land use, and soils, the GIS might produce a new map layer or overlay that ranks the wetlands according to their relative sensitivity to damage from nutrient runoff.
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What is GIS?
 The land use and land cover map for the two areas shows that the area is partly developed. View showing a half-mile buffer zone drawn
around the service area of the Somers Water
Company.
A soils map stored in a GIS database. Numbers
indicate the type of soil.
The wetlands in the study area ranked according to
their vulnerability to pollution on the basis of
combination of factors evaluated by GIS.
What is GIS?
 A critical component of a GIS is its ability to produce graphics on the screen or on paper to convey the results of analyses to the people who make decisions about resources.  Wall maps, Internet‐ready maps, interactive maps, and other ggraphics can be generated, allowing the decision makers to p
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visualize and thereby understand the results of analyses or simulations of potential events
What is GIS?
 The land use and land cover map for the two areas shows that the area is partly developed. Land use
View
showing
and land
a half-mile
cover data
buffer
forzone
the area
drawn
around the
bounded
byservice
a half-mile
areabuffer
of the zone
Somers
around
Water
the
Company.
water
company service area.
Land use and land cover data for the area
bounded by a half-mile buffer zone around the
water company service area.
 The developed areas were eliminated from further consideration.
What is GIS?
 The U.S. Geological Survey (USGS), in a cooperative project with the Connecticut Department of Natural Resources, digitized more than 40 map layers for the areas covered by the USGS Broad Brook and Ellington 7.5‐minute topographic quadrangle maps.  This information can be combined and manipulated in a GIS to address planning and natural resource issues. What is GIS?
 Some of the streams in the study area were known to be unusable as drinking water sources. To avoid pulling water from these streams into the wells, 100‐meter buffer zones were created around the unsuitable streams. Buffer zones of 100 meters are drawn
around polluted stream in the water
service area.
CIVL 1101
What is GIS?
What is GIS?
 The map showing the buffered zones was combined with the land use and land cover map to eliminate areas around unsuitable streams from the analysis
Buffered streams area subtracted from
Buffer
zones of 100
meters
are the
drawn
areas previously
selected
with
land
around
stream
use
andpolluted
land cover
data.in the water
service area.
What is GIS?
 Point sources of pollution are recorded by the Connecticut Department of Natural Resources. These records consist of a location and a text description of the pollutant.
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What is GIS?
 This information was combined with the previous two map layers to produce a new map of areas suitable for well sites
A
new map
created
in a GIS
eliminating
Buffer
zonesisof
500 meters
areby
drawn
the
buffered
sources
of pollution
from the
around
the point
sources
of pollution.
previously selected areas
What is GIS?
 The map of surficial geology shows the earth materials that lie above bedrock.
 Since the area under consideration in Connecticut is covered by glacial deposits, the surface consists largely of sand and ggravel, with some glacial till and fine‐grained sediments. ,
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Points sources
Buffered
streams
of pollution
area subtracted
in the water
from
areas previously
service
area are identified
selected with
and the
entered
land into a
use and land cover data.
GIS.
What is GIS?
 To avoid these toxic areas, a buffer zone of 500 meters was established around each point.
What is GIS?
 Of these materials, sand and gravel are the most likely to store water that could be tapped with wells. Areas underlain by sand and gravel were selected from the surficial geology map.
Points zones
Buffer
sources
of of
500
pollution
meters in
are
the
drawn
water
around the
service
areapoint
are identified
sources ofand
pollution.
entered into a
GIS.
Selection areas of sand and gravel from
the map of surficial geology.
CIVL 1101
What is GIS?
What is GIS?
 Theses data were combined with the results of the previous selections to produce a map consisting of: (1) sites in under‐
developed areas underlain by sand and gravel, (2) more than 500 meters from point sources of pollution, and (3) more than 100 meters from unsuitable streams.
Map produced by combining the areas
composed of sand and gravel with previous
Selection areas of sand and gravel from
selection
the map of surficial geology.
What is GIS?
 A map that shows the thickness of saturated sediments was created by using the GIS to subtract the bedrock elevation from the surface elevation.
A bedrock elevation subtracted from surface
Map produced
by combining
thethickness
areas
elevation
by a GIS
to show the
of
composed of sand
and gravel with previous
water-saturated
sediment.
selection
What is GIS?
 For this analysis, areas having more than 40 feet of saturated sediments were selected and combined with the previous overlays.
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What is GIS?
 The resulting site selection map shows areas that are undeveloped, are situated outside the buffered pollution areas, and are underlain by 40 feet or more of water‐saturated sand and gravel.
Potential sites with saturated thickness of
sediments greater than 40 feet.
What is GIS?
 Because of map resolution and the limits of precision in digitizing, the very small polygons (areas) may not have all of the characteristics analyzed, so another GIS function was used to screen out areas smaller than 10 acres.
Potential sites with saturated thickness of
sediments greater than 40 feet.
What is GIS?
 The final six sites are displayed with the road and stream network and selected place names for use in the field.
Potential water well sites, roads,
streams and place names.
Potential
with saturated
of
A bedrocksites
elevation
subtractedthickness
from surface
sediments
greater
than
40 feet.
elevation by
a GIS to
show
the thickness of
water-saturated sediment.
Potential sites with saturated thickness of
sediments greater than 40 feet.
CIVL 1101
What is GIS?
What is GIS?
 Site selection analysis has many common applications, include‐
ing transportation planning and waste disposal site location
Potential water well sites, roads,
streams and place names.
What is GIS?
 The technique is particularly useful when several physical factors must be considered and integrated over a large area.
Potential water well sites, roads,
streams and place names.
What is GIS?
 More detailed information can be found about this presentation at: http://egsc.usgs.gov/isb/pubs/gis_poster/
Any Questions?
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