GIS in Public Health-- or --

As the World Turns

Lois M. Haggard, Ph.D.

March 17, 2003

CFHS Program Managers Meeting

Outline

Brief review of GIS constructs

Spatial analysis and public health examples

“How to” - local resources for mapping your data

Disclaimer

I am not a GIS specialistI learned much of what I know in

preparation for this presentation!I am glad to share what I have learned, and

we can go forward together.

Basic Theory and Constructs

GIS Defined: A Geographic Information System consists of

all the computer hardware, software, personnel and data that are required to map and analyze spatial data.

A popular GIS software provider is ESRI (Environmental Systems Research Institute). They produce ArcView (desktop version), ArcIMS (for Internet applications), and ArcExplorer (freeware), among others.

Basic Theory and Constructs

GIS versus GPS GIS is not GPS - but GPS is used by GIS GPS stands for “Global Positioning System,”

which is a system of satellites circling the Earth, and the devices that interpret the data from those satellites, providing coordinates on the Earth’s surface. (GPS “Geocodes” your position on the Earth’s surface.)

Basic Theory and Constructs

Purpose of GIS in Public Health Descriptive epidemiology -

• Person• Place• Time

Maps used in public health generally depict how events that happened to persons during a particular time window are distributed over geographic space.

CDC URL for GIS in public health -- http://www.cdc.gov/nchs/gis.htm

Basic Theory and Constructs

Purpose of GIS in Public Health Disease and injury events have spatial

associations we may want to be aware of. • Infectious diseases spread from person to person• Environmental exposures (e.g., cancer downwind

from nuclear testing)• Heath care utilization is related to proximity to

facilities• Lifestyle factors can be related to environment• Health status is related to other social factors (e.g.,

income, education) that are spatially related.

The “Global” Perspective

-NEWS FLASH-

Earth Not Flat!

-- But maps ARE --

A location on the Earth is communicated in latitude and longitude.

A location on a map is communicated using Cartesian coordinates (x, y, & sometimes z)

Cartesian Coordinates

Projections and Distortion

Map projections project the Earth's surface onto a flat plane.

There are numerous types of projection, each of which distorts some parameter of the Earth's surface be it distance, area, shape, or direction.

Projection decisions always represent tradeoffs between different types of distortion and convenience.

Mercator Projection

Mercator Projection

Transverse Mercator

Spatial Analysis

Geocoding Definition: Transforming a location on the

Earth’s surface into x and y coordinates so it may be represented on a map.

Common example: Geocoding addresses - What are the x and y coordinates for our address: 288 North 1460 West?

• Which projection?

Spatial Analysis

Overlays

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Spatial Analysis

“Themes” Definition: A feature, layer or phenomenon

represented on a map. Examples:

• brain cancer

• census tract boundaries

• pollution plume

• city streets

• water systems in London in 1856

Spatial Analysis

“Themes” (cont’d) Cancer Examples:

• cancer screening

• cancer incidence

• cancer cases detected at late stage

• cancer survival

• cancer mortality

Spatial Analysis

“Attributes” Definition: Characteristics of the feature being

mapped. Examples:

• street starts at point x1, y1 and travels to point x2, y2

• color is blue• name labels• death rate (for polygon) is 78.2• contour lines represent 250 vertical feet elevation• contour lines represent logarythmic

increases/decreases in disease rate

Spatial Analysis

Types of Maps Isopleth (points and contours, raster)

• Clusters

• Raster algebra, kriging

• Public health applications

Clinton/Sunset TCE Plume With Shifted Cancer Cases and Ownership Polygons

Spatial Analysis

Isopleth Pros and Cons Pros

• You can get more precise view of phenomenon Cons

• You need more complex “raster algebra” to compute rates

Spatial Analysis

Types of Maps Chloropleth (polygons, vector-based)

• Common ploygons (county, LHD, census tract, ZIP code)

• Boundaries, Centroids

• Public health applications

vector

Spatial Analysis A polygon is a many-sided geometric shape.

GIS software records it as a series of nodes and vectors. Together the nodes and vectors are called a “shape file.”

node

geographic centroid

population centroid

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B i r th t o M o m s 1 0 -1 7 L o w e r t h a n S ta teN o D i f f e r e n t th a n S ta teH ig h e r t h a n S ta te

Percentage of Births That Were Born to Adolescent Mothers by Whether the Rate Was Higher, Lower, or Not Different (Statistically) from the State Rate.

Utah, 1994-96.

Percentage for a small areas was considered different from the state rate if its 95% confidence interval did not include the state rate.Small area designation was based on residence of mother.Data Source: Utah Department of Health, Bureau of Vital Records.

Spatial Analysis

Chloropleth Pros and Cons Pros

• Computation of rates is simple (providing you have population denominators for areas)

Cons• Not as precise a view

– The smaller the area, the more spatial information, but we’re limited by sparse data and lack of population data that matches numerator data.

– A cluster could lap two areas or appear in a populated area and be “washed out” by the large population.

A Geographic Information Analysis of

Urban Infant Mortality Rates

Gerard Rushton 1 , Diane Krishnamurti 2 , Rajesh Krishnamurthy 1 and Hu Song 3

1. Department of Geography, The University of Iowa, Iowa City, Iowa 52242

2. Iowa Birth Defects Registry, The University of Iowa, Iowa City, Iowa 52242

3. Iowa Department of Public Health, Des Moines, Iowa 52319

http://www.uiowa.edu/~geog/health/

Spatial Pattern of Infant Deaths

Infant Births in Same Area

Raster Grid, or Lattice

Geo Areas Correspond to Grid

Contour Lines for Infant Death Rates & Census Track Overlay

Infant Mortality Rates by Census Tract

New York City Maps

I was just in NYC, and saw these maps. I think I’ll copy some ideas for IBIS...

On Your Mark, Get Set...

Software ArcView 8.2

• Runs on Windows NT, 2000, XP• $1,500 for a single-user, stand-alone license (UDOH

has it on the network. You still need a license, but I’m not sure about the cost.)

URL for ArcView and other ESRI products: http://www.esri.com/

There are other software providers, but ArcView is the product we’ve always used in OPHA.

On Your Mark, Get Set...

Data to Represent Themes Geocoded themes of interest (e.g., births,

residence of persons with a given disease) Shape files Overlays - Many available through the state’s

Automated Geographic Resource Center (AGRC) at maps.utah.gov

Considerations

How many categories? (translates into how many color shades)

Which colors to use? (hot colors like red often used to represent areas of concern, don’t forget red/green color-blindness, will it print or photocopy in B&W?)

General legibility (I’ve shown various examples, some better than others)

Mapping on IBIS-IRV

Utah’s 42 Community Health IndicatorsMapped as chloropleth maps (as data will allow):

LHD Small Area County

With interactive overlays user can turn on and offZoom feature will allow view of entire state, or

small area

Timeline for IBIS Maps

Map prototype - done

IBIS Map Prototype

Timeline for IBIS Maps

Map prototype - doneDefine community health indicators - done

Community Health Indicators1. Injury and Violence 7. Access to Health Care

a- Motor Vehicle Deaths (810-819) a- Health Insurance Coverageb- Homicide and Legal Intervention (E960-E969) b- Regular ongoing source of primary carec- Unintentional Injuries (E800-E869, E880-E929) c- Prenatal Care in 1st Trimester

2. Mental Health d- Hosp for asthma among childrena- Suicide (E950-E959) e- Hosp for diabetes among adultsb- Health Status: Mental Health Last 30 Days f- Hosp for pneumonia among elderly

3. Lifestyle Risk g- Mammography Screening Ratea- Tobacco Use 8. Chronic Conditionsb- Overweight or Obese (adults) a- Lung Cancer Deaths (162)c- Physical Activity b- Stroke Deaths (430-438)d- Binge Drinking c- Female Breast Cancer Deaths (174)e- Adolescent Substance Abuse d- Colorectal Cancer Deaths (153-154)

4. Responsible Sexual Behavior e- Heart Disease Deaths (402, 410-414, 429.2)a- HIV/AIDS Incidence ( 042-044) f- Cancer Deaths b- Reported Early Syphillis Cases g- Reported Hepatitis A Casesc- Reported Gonorrhea Cases h- Reported Tuberculosis Cases (Incidence)d- Reported Chlamydia Cases 9. Healthy Birthse- Unintended Pregnancies a- Infant Mortalityf- Births to Adolescents 15-17 b- Low Birth Weight

5. Environmental Quality 10. Children in Povertya- Air Quality (Ozone ̂EPA Std) a- Childhood Povertyb- Children Exposed to ETS 11. Overall Health Statusc- Reported Salmonella Cases (Incidence) a- Life Expectancy at Birthd- Reported E Coli O157:H7 b- Health Status: Physical Health Last 30 Days

6. Immunization a- 4:3:1:3:3b- Influenza (adults)

Timeline for IBIS Maps

Map prototype - doneDefine community health indicators - doneMove existing graphics to new SVG system

for better-looking charts and maps - end of March/beg of April

Sizing Bitmaps

Timeline for IBIS Maps

Map prototype - done Define community health indicators - done Move existing graphics to new SVG

system for better-looking charts and maps - end of March/beg of April

Get data on IBIS for maps - JuneGet SVG map views attached to data and

working - July

Thank You!