Introduction to Geographic Information Systems GIS

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Introduction to Geographic Information Systems
(GIS)
Note this presentation includes material from
Dr. Dionne Law, Dr. Marc Serre, and others.
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Organization of presentation

• History of GIS
• Basics of GIS
• GIS Approaches to Investigations
• Limitations
• GIS data at the New Jersey Department of
  Environmental Protection

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Part I History of GIS
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History of GIS

• Battle of Yorktown
• French cartographer had hinged overlays to show
  troop movements
• Irish Railway Commission (mid 1800s)
• Atlas showing overlay of population, traffic
  flow, geology, topography on same base map
• John Snows Cholera Investigation

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John Snows Cholera Investigation
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History of GIS
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History of GIS
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History of GIS
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Summary

• GIS has been around a long time
• Well established tool in cartography, land
  resources, geography, earth sciences, ecology,
  planning, business, many other fields
• Only recently has GIS been discovered by Public
  Health

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Part II Basics of GIS
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Geographic Information Systems (GIS)

• GIS facilitates visualization and analysis of
  spatial data
• Spatial data are stored in map layers

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Coordinate Systems

• Spatial data are referenced to locations on the
  earths surface using coordinate systems
• Ensure all map layers share a common coordinate
  system
• Recognized global coordinate systems consist of
• A Spheriod a mathematical description of the
  earths shape
• A Map Projection a mathematical conversion from
  spherical to planar coordinates

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Map Projection
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Map Projection
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Scale

• Tells how map distance relates to real world
  distance
• Map Scale ratio of map distance to actual
  ground distance
• 110,000 (1 map cm 10,000 real cm)
• Small scale (1100) vs. large scale (110)
• Scale Bar graphic display of map scale

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Resolution

• The accuracy with which a given map scale can
  depict the location and shape of map features
• Larger the map scale, the higher the resolution
• As map scale decreases, resolution diminishes and
  feature boundaries are smoothed, simplified, or
  not shown at all.
• Rule of thumb error 2 of map scale
• Resolution plays a large role in GIS, especially
  in raster-based modeling

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Raster-based GIS

• Data stored in a regularized grid of cells
  covering an area
• Grid cells called picture elements or pixels
• Nodes, Arcs, Areas

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Vector-based GIS

• Image and data stored separately
• Data attribute table
• Image points, lines, polygons

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Summary

• GIS facilitates visualization and analysis of
  spatial data
• Spatial data are stored in map layers
• Most GIS programs are raster- or vector- based
• Raster - data and image stored together in
  regularized grid made of pixels
• Vector - data and image stored separately
  points, lines and polygons

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Part III GIS Approaches Investigations
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Approaches to GIS

• Step 1 Define the question
• Step 2 Determine data needs
• Step 3 Collect and prepare data
• Step 4 Analyze data

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Step1 Define the Question

• What areas are vulnerable to a 100 year flood?
• How many people live in these areas?
• Where do we need to implement locally based flood
  mitigation efforts?

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Step 2 Determine data needs

• What map layers are needed?
• population estimates, streets, census tracts,
  county, digital elevation model, land cover, 100
  year floodplain, flood control data, climatic
  data?
• What data is already available?
• population estimates, streets, census tracts,
  county, digital elevation model, land cover, 100
  year floodplain?, remote sensing data?
• What data needs to be collected, or digitized?
• historic flood damage, flood control and
  mitigation data, location of emergency services

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Step 3 Prepare spatial data

• Existing digital data
• complete, clean, up-to-date, formatted,
• share common projection and coordinate system
• pieced together, clipped
• New digital data
• geocoding damage address matching, GPS
• digitizing
• manipulate existing data

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Step 4 Data Analysis

• Manipulation
• Clip and paste together area of interest
• Construct watershed from digital elevation models
• Construct drainage/river network

• Overlays
• Superimpose two or more map layers
• For display and analysis purposes
• Overlay census data with floodplain data

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Step 4 Data Analysis

• Buffers
• Identify areas 5km, 10km, 15km from river network

• Queries
• Estimate potential number of people living in
  high flood risk areas

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Step 4 Data Analysis

• Network Analysis
• Construct evacuation routes
• Estimate travel times for emergency response
  vehicles

• Modeling
• prediction storm path
• estimation damage estimates for structures and
  infrastructure
• simulation emergency preparedness

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Summary

• GIS can enhance emergency preparedness and
  response locally, nationally, globally
• Strengthen data collection, management and
  analysis
• Monitor changes over time
• Develop early warning systems
• Plan and monitor response programs
• Communicate to decision makers and the public

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Part IV Limitations
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Three good rules to follow

• Never assume a spatial database is free of error.
  
• Develop methods for assessing data quality
  whenever possible.
• Always get the metadata file.
• - describes content and quality of spatial
  database

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Limitations

• Accuracy and completeness
• spatial data
• non-spatial data
• Currency of data
• When were the data collected?
• Last updated?
• Time sensitive?
• Appropriate for the analysis?

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Limitations (continued)

• Geocoding
• Address matching
• urban vs. rural environments
• Representation of disease
• residential address vs. social location
• Precision
• Scale of source map
• Modifiable Area Unit Problem
• spatial distribution of a factor changes
  significantly depending on how it is aggregated
• census tract vs. zip code vs. county

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Limitations (continued)

• Disease etiology
• Proximity vs. exposure
• Confidentiality
• Use smaller-scale maps
• Remove the street network on the map
• Displace point features

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Summary

• Need to be aware of the sources of error and
  limitations associated with GIS.
• However
• Errors can be minimized
• Most limitations are function of data available,
  not GIS

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Conclusion

• GIS is an investment
• hardware, software, and know-how costs
• GIS is a powerful multidisciplinary tool that
  presents opportunities for collaborations and
  coordination between government, academia,
  industry, and the public

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Part VGIS data at the New Jersey Department of
Environmental Protection
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New Jersey Department of Environmental Protection

• NJDEP
• http//www.nj.gov/dep/
• NJDEP - GIS
• http//www.nj.gov/dep/gis/
• NJDEP - Water Monitoring Standards
• http//www.state.nj.us/dep/wmm/
• NJDEP - Water Monitoring Standards Bureau of
  freshwater biological monitoring
• http//www.state.nj.us/dep/wmm/bfbm/

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NJDEP - GIS

• The NJDEP GIS Department (http//www.nj.gov/dep/
  gis/)
• provides GIS files for state administrative
  areas, hydrology, geology, land use, etc., such
  as
• Counties
• Digital Elevation Grid
• Hydrography
• Watersheds
• Water Quality Monitoring Stations

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NJDEP - Water Monitoring Standards

• The NJDEP Office of Water Monitoring Standards
• (http//www.state.nj.us/dep/wmm/)
• oversees the Bureau of Fresh Water and Biological
  Monitoring .
• This bureau is in charge of monitoring the
  ambient conditions of the state's fresh and
  ground water resources. This monitoring includes
  
• regular sampling through a statewide network
  consisting of 115 surface water monitoring
  stations,
• 820 benthic macroinvertebrate biological stream
  monitoring stations,
• 100 fish assemblage biological stream monitoring
  stations, and
• 150 ground water stations.

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The Raritan Basin in New Jersey
54 Monitoring Stations Across 3 Watershed
Management Areas
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Water quality data for the Raritan river basin

• Monitoring Station Data was gathered for 3
  Watershed Management Areas (WMA)
• N/S Branch Raritan (8)
• Lower Raritan (9)
• Millstone (10)
• Dataset was obtained from two sources
• NJ DEP/USGS Water Quality Network1
• EPA STORET Database2
• Dataset contains 6 water quality parameters
• Discharge, Dissolved Oxygen, Ammonia,
  NitrateNitrite, Phosphate, Temperature
• Additional Parameters can be added as needed
• Measurements were taken approximately 4
  times/year from 1990-2002
• Values were log-transformed depending on
  distribution

1http//waterdata.usgs.gov/nj/nwis/qw
2http//www.epa.gov/STORET
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Phosphate data (mg/L) over the Raritan
The movie of the data illustrate its space/time
variability
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Challenges

• Sparse network of monitoring sites
• Monitoring data may have varying measurement
  errors
• High variability of the data over space and time
• The relevant spatial distance metric is a
  combination across land and along river
  metric
• Limited resources prevents use of deterministic
  water quality models, but a stochastic version
  may provide useful knowledge

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Conclusion

• In the State of New Jersey, GIS provides a set of
  basic functions allowing to query and extract
  monitoring data with health concerns. The arcGIS
  software will provide the necessary basic
  functions of GIS.
• The monitoring data varies over space and time,
  therefore we need advanced functions of Temporal
  GIS to map their distribution at unsampled
  locations. The BMElib software of space/time
  Geostatistics will provide the necessary advanced
  functions of Temporal GIS

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ESRI arcGIS at UNC

• UNC GIS software includes ESRI arcGIS version
  9.0, 9.1, 9.2
• Technical Support http//www.unc.edu/atn/gis
• research_at_unc.edu (919) 962-HELP
• Data Sources http//gis.unc.edu/
• Amanda C. Henley, GIS Librarian
  amanda.henley_at_unc.edu [phone]