1 HGIS011006

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Geographic Information System (GIS) and Public Health 江博煌 國家衛生研究院 衛生政策研發中心 科技管理師 1/10/2006 衛生地理資訊研討系列

3S 科技: 

3S 科技 遙測 Remote Sensing (RS) 全球衛星定位 Global Positioning System (GPS) 地理資訊系統 Geographic Information System (GIS)

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Traditional GIS Design A computerized system for the storage, analysis, and display of geographically referenced information: Data Layers (example) Population Transportation Services

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Thiessen Polygons Concentric Circles surrounding points have been used in the past for analysis. This has 2 limitations – circles overlap and also leave gaps (see top figure). An improvement over this is the Thiessen Polygon (see bottom figure). In Thiessen polygons, a transect is drawn between two points creating the “best-fit polygon.” Overlap Gap Theissen Polygons Concentric Circles

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Distance Decay

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Selected Analytical Methods for Use Public Health Vector Methods Raster Methods Object-Oriented Methods Statistical Methods

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Vector GIS Source: http://www.geography.hunter.cuny.edu/courses/gis2/lectures/lecture2/vector.gif

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System Development - Atlas of Health (http://atlas.nhri.org.tw)

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System Development - Atlas of Health (http://atlas.nhri.org.tw)

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System Development - Area Resource File (ARF) (http://hgis.nhri.org.tw)

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CDC 類鼻疽病例分佈

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http://www.cdc.gov/hiv/graphics/images/L206/L206-14.htm US CDC Use of GIS

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US AIDS Cases Animation http://www.cdc.gov/hiv/graphics/images/dotmaps/dotmapan.htm

Bird Flu: 

Bird Flu

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Color coded circles for wild bird H5N1:(confirmed or suspected in confirmed location) May = Blue June = Orange July = Yellow August 15 = Green August 31 = Red September = Purple Current = White Green or Red squares are unconfirmed bird deaths in unconfirmed locations

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Raster GIS Data Model Source: http://www.geography.hunter.cuny.edu/courses/gis2/lectures/lecture2/fig210.gif

Raster Methods: 

Raster Methods Interpolation Density

Raster Interpolation: 

Raster Interpolation IDW (Inverse distance weighted) Search Neighborhood Global polynomial Local polynomial Radial basis functions Kriging

Raster Interpolations: Kriging: 

Raster Interpolations: Kriging Definition: Kriging creates a surface of predicted values using mathematical as well as statistical models. Kriging takes spatial autocorrelation into account Examples: Continuous surface of population at risk Model environmental risk factors such as toxic soil Continuous surface of disease and disease diffusion

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Spatial Interpolation Method for Identifying Heavy Metal Soil Contamination Areas 行政院環境保護署 國家衛生研究院 環境衛生與職業醫學研究組 國家衛生研究院 衛生政策研發中心

Data: 

Data 2002 ChungHua city topsoil monitoring data (1474 topsoil sub-sample) 2004 ChungHua City health survey data (500 human sample – additional 500 in 2005)

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Sample Statistics and Threshold Limits* (N=1,474)

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Ordinary Kriging (a) Cd (b) Cr

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Simple Kriging (a) Cd (b) Cr

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Spatial Interpolation Method for Identifying 台南安順 Sediment Contamination Areas 行政院環境保護署 國家衛生研究院 環境衛生與職業醫學研究組 國家衛生研究院 衛生政策研發中心

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Example: Simple Density Source: http://www.geo.hunter.cuny.edu/%7Emarcofj/gis2/lab3bis/lab3bis.html

Other Useful Functions: 

Other Useful Functions The CS137 (radioactive isotopes) contamination and thyroid cancer data was supplied courtesy of the International Sakharov Environmental University.

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Cellular Automata Agent-Based Modeling Object Oriented Methods

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Cellular Automata: SLEUTH Slope, Land-use, Exclusion, Urban extent, Transportation, Hillshade Urban Sprawl Model using CA developed by Dr. Keith Clarke, University of California – Santa Barbara Uses historical data to simulate present day urbanization Current work: Run the model into the future Simulate alternative futures Compare across scale and cities Apply to Urban Dynamics to cities Source: Keith Clarke, http://www.ncgia.ucsb.edu/projects/gig/v2/About/ppt-pres/gistw.pdf

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Example: Cellular Automata SLEUTH Model Source: Keith Clarke, http://www.ncgia.ucsb.edu/projects/gig/v2/About/ppt-pres/gistw.pdf

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Cluster Detection Geographical Analysis Machine (GAM) Spatial Scan Statistic DYCAST Statistical Models

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Cluster Detection: GAM Geographical Analysis Machine (GAM) Developed by Openshaw, Charlton and Craft (1988)* to assess Childhood Acute Lymphoblastic Leukemia GAM includes a test for statistical significance of clusters Steps: Draws fine grid around study region Draws different-sized circles around the centroid of each grid Determines if incidence inside each circle is higher than expected based on the “typical” rate of illness in the population * Openshaw, S., Charlton, M., & Craft, A. (1988). Searching for Leukemia Clusters Using a Geographic Analysis Machine. Papers of the Regional Science Association. 64: 95-106.

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Example: GAM Distribution of Significant Acute Lymphoblastic Leukemia Circles * Openshaw, S., Charlton, M., & Craft, A. (1988). Searching for Leukemia Clusters Using a Geographic Analysis Machine. Papers of the Regional Science Association. 64: 95-106.

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Cluster Detection: SatScan Spatial Scan Statistic (SatScan) – FREE! NOT a “true” GIS as it does not have mapping functions but results can be transferred into a GIS for mapping. Developed by Kulldorf, Feuer, Miller and Freedman (1997)* to test for Breast Cancer Clusters in the Northeast USA. Similar to GAM but uses Monte carlo Simulation to determine if cases are solely due to random chance. Tests include: Poisson – Case clustering based on Population at Risk Bernoulli – Case clustering based on Control group Space-Time Permutation – Case clustering based on Time * Kulldorff M. and Information Management Services, Inc. (2003). SaTScan v4.0: Software for the spatial and space-time scan statistics. Online Internet. http://www.satscan.org/

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Dynamic Continuous Area Space-Time (DYCAST) Hunter College, CUNY (2003), to assess areas of high risk of West Nile in NYC. A grid is meshed across NYC while a roving window moves across the grid. At each cell’s centroid, the Knox statistical method checks the probability that dead crows found within the window are statistically close in space (0.25 miles) and time (3 days). Successfully predicted human cases of West Nile in 2001 in NYC. NYC Department of Health used it in 2002 to target areas for spraying pesticide to reduce mosquito population. * Theophilides, C. N., Ahearn, S. C., Grady, S., Merlino, M. (2003). Identifying West Nile Virus Risk Areas: The Dynamic Continuous-Area Space-Time System. Am. J. Epidemiol. 157: 843-854

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Source: http://www.geography.hunter.cuny.edu/~yllik/gis2/lectures/lecture6/lecture6.html DYCAST

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Source: http://www.geography.hunter.cuny.edu/~yllik/gis2/lectures/lecture6/lecture6.html DYCAST

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Health Informatics R&D (HIRAD) Research Group - Health GIS (HGIS) Research Lab Thank You!