Agile GIS : Building applicationspecific spatial analytic software from freely available software tools

Transcription

1 Agile GIS : Building applicationspecific spatial analytic software from freely available software tools Lance A. Waller, Andrew B. Barclay Department of Biostatistics Rollins School of Public Health Emory University lwaller@sph.emory.edu Partially supported by NIEHS Grant 2 R01 ES A1

2 Outline Lean and agile software tools. Two motivating examples: Environmental justice. Sea turtle nesting patterns. Conclusions.

3 Making methodology applicable: We want a software tool that a) accesses GIS location/attribute data, b) performs GIS operations, AND c) calculates/plots statistical quantities. GIS does a) and b) easily. Statistical packages do c) easily. How do we get both?

4 Lean and agile software Close tie between user and developer. Use toolbox of objects and functions to address application ( agile ), but little else ( lean ). End user: implements method accurately and efficiently, BUT doesn t master GIS or statistical packages.

5 Illustration of lean and agile GIS Statistical Package Lean and agile alternative

6 Advantage of lean and agile Shorter learning curve. For example, put user of (software A) behind the wheel of (software B)

7 Ingredients (GIS component): Minimal functionality: Location/attribute data queries Layering and buffering GIS Toolkits ( GRASS (C++), Berkeley GIS Viewer, GISToolkit, OpenMap, Jshape, GeoTools. Why Java? Lightweight Object-oriented Browser platform

8 Ingredients (Statistics/plotting): Tools providing numerical computing power (e.g. simulation) Tools graphical display of results Tools linking statistical results to geographic displays Components (e.g. Java Beans, OmegaHat, R)

9 Two examples of lean agility Environmental justice Map census demographics Map environmental hazards Compare exposure distributions for different subpopulations Fishing pier vs. sea turtles Map sea turtle emergences Map fishing pier Compare emergence patterns around pier.

10 Child Welfare in Georgia Type mix of substantiated incidents of child abuse by county. Locations of foster children. Basic question: What is the geographic distribution of (some statistic of interest)?

11 Environmental Justice Environmental Justice: Do subgroups of the population bear a disproportionate impact of environmental hazards? LULU? NIMBY! One question of interest: Assess disparate impact due to different sites. Compare distribution of exposures between subgroups. Question: Who is exposed where?

12 Basic GIS operations: Layering

13 Basic GIS operations: Buffering Find areas within a userspecified distance of: points lines areas Buffers around an area Buffers around a line feature

14 EJ and GIS Typical GIS assessment of environmental justice: Layer census data (population counts in tracts), emission locations (TRI sites). Buffer for some radius (e.g., 1 km), report population proportions inside buffers ( exposed ) and outside buffers ( unexposed )

15 Allegheny County, PA 499 census tracts (1990 Census). Compare census reported black and white subpopulations. 200 air emission sites in EPA s Toxic Release Inventory (TRI) for Allegheny and surrounding counties for 1990.

16 Allegheny County, PA 1990 Exposed Race Category Black White Allegheny County Everyone Site in Tract 1km buffer 2km buffer 3km buffer 4km buffer 11.20% 87.56% Tract data 12.01% 87.09% 12.56% 86.49% 13.63% 85.16% 13.13% 85.57% 12.23% 86.46%

17 Other options: Waller, Louis, and Carlin (1997,1999) compare the exposure distributions between subgroups. Exposure surrogate: inverse distance from tract centroid to closest TRI site. Plot cumulative distributions of exposure surrogate for each subpopulation. Illustrates whether subpopulations experience different exposure profiles.

18 Example: Environmental Justice Maps census boundaries. Layers TRI sites and calculates distances. Click on map, CDFs by subgroup plotted. Mouse to find impact on particular tracts. Visually identifies sites by disparate impact with respect to exposure surrogate.

19 Sea Turtle Nesting Patterns Juno Beach, FL Premier nesting beach for endangered loggerheads. 990 ft. fishing pier Assess impact of pier on nesting patterns. 8,000-10,000 GPS coordinates per year Question: Do emergence patterns differ between years?

20 The life cycle of sea turtles tofino.ex.ac.uk/euroturtle/ biology/lifec.htm

21 Juno Beach, Florida Palm Beach County Nesting beach for loggerhead and green turtles. Nesting season: May-September. Lighting restrictions in place. 990-ft. fishing pier constructed Permitting requires impact assessment. Palm Beach Co. Environmental Resources Management in charge of assessment.

22 Traci and Bud at the pier

23 Our data Volunteers from the Marinelife Center, Juno Beach, Florida patrol beach each morning during nesting season.

24 How do you find a turtle nest? Females emerge from ocean, and leave trackways. Not all emergences result in nests ( nonnesting emergence or false crawl ).

25 Data (continued) Global Positioning System (GPS) readings of each observed crawl. 10,240 GPS ed emergences in 1998 (12,183 observed). 8,786 GPS ed emergences in ,614 GPS ed emergences in 2000.

26 A day on the beach

27 Data (continued) Differential GPS (referenced to Coast Guard Station): submeter accuracy. Measured as feet from northern reference point. Attribute data: species, nesting/nonnesting, predation.

28 Juno Beach GIS data Y Y Y YY Y Y Juno Beach Turtle Nesting Data Layers: Photographs GPS Emergences INB Zones

29 Statistics Consider emergence locations along a line. Want intensity function (number of emergences per unit area). Estimate intensity for each year via kernel estimators. H 0 : Intensities the same for each year. H 0 : ratio = 1 everywhere along beach.

30 Significance Monte Carlo envelopes. Random labelling. Keep emergence locations, randomly assign year to each location. Calculate ratio of intensities to assess amount of wiggle under H 0.

31 Intensities Log(ratio of intensities)

32 Software Software: Input:.dbf file for a particular year. Processing: R + splancs (spatial point process add on library) scan for location and species information in.dbf file calculate intensities, ratios, and Monte Carlo confidence bands. Output: Bitmap figures that can be layered into ArcView GIS with aerial photographs, and GPS locations.

33 GPS data to.dbf file Extract species, location Extract species, location Linearize beach (loess) Project points to curve Kernel estimation Ratio calculation Random labelling simulations Create.bmp figure.bmp to ArcView for display

34 Proof of concept: Bud applies software developed for Juno Beach to assess impact of beach renourishment project on different stretch of beach. Conclusion: Turtles move south of impacted area. Bud s graphic >>>>>>

35 Pros to agile GIS Provides targeted (lean) software for user. Particularly useful for repeated tasks. Built from components rather than forcing large package to do something it wasn t designed to do. Each user uses majority of functionality of software. Free and open-source software (

36 Cons to agile GIS Constantly under development. Multiple tasks? Lower level programming for developers. Free software.

37 Conclusions Result: Agile GIS tools for environmental justice/wildlife monitoring. Developing idea. Brings methodology directly to end user. Attractive alternative to mastering two domains.