Larry Stanislawski , Michael Howard

1. Larry Stanislawski, Michael Howard Center of Excellence for Geospatial Information Science (CEGIS), United States Geological Survey, Rolla MO Marc-Olivier Briat, Edith Punt Esri, Inc., Redlands CA Cynthia Brewer Department of Geography, Pennsylvania State University, Unversity Park PA Barbara Buttenfield Department of Geography, University of Colorado-Boulder, Boulder CO Density-Stratified Thinning to Support Automated Generalization of Transportation 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

2. Outline • Esri Thin Road Network Tool • Density-stratified Thinning • Results of Stratified Thinning • Summary Statements and Future Work 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

3. Cartography Geoprocessing Toolbox • ArcGIS 10 introduced contextual generalization tools that consider relationships between features from multiple layers • Maintain representative patterns, density, and character • Resolve conflicts between symbolized features

4. Esri Thin Road Network tool • Maintain pattern and density while retaining connectivity • Keep significant roads only • Balanced by road classification • Retain specific features by locking • Visibility controlled by attribute, easy to modify

5. Esri Thin Road Network Tool Inputs: Road network features, Minimum length, Invisibility field, and Hierarchy field Marks features for elimination to create a simplified pattern of roads that maintains connectivity, representative pattern, and density • Limitations of Thin Road Network Tool • Preprocessing • A single minimum length can homogenize local density variations (more than expected) • Difficult to set tolerance values for tool 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

6. Preprocessing for Thin Network Tool • Road network features • Projected coordinate system • Remove coincident features • Transfer names to retained features • Multi-part features to single-part features • Ensure features are split at intersections • Hierarchy field • Compute importance values based on road class (and names where class is missing) 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

7. Test Data: Four Subbasins in Rural Iowa and Part of Atlanta Metropolitan Area • Four subbasins in Iowa: • ~24,000 sq km • Rural midwest agricultural area • Des Moines ~580,000 persons • Over 109,000 road features • Nearly 36,000 km of roads • Part of Atlanta MSA • ~10,000 sq km • Dense urban area • Atlanta MSA pop. ~5.4M • Over 393,000 road features • Nearly 49,000 km of roads Road data from transportation layer of USGS Best Practices (BP)database 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

8. Test Methods • Subdivide data into density classes • Iowa: < 1.50 and > 1.50 km / sq km, min. polygon area = 45 sq km • Atlanta: < 2.50, 2.50 to 4.50, and > 4.50 km / sq km, min. polygon area = 45 sq km. • Determine 100K target density estimate for each class using Radical Law • Run thin network tool multiple times to find which minimum length comes closest to the 100K target density for each density class • Extract visible lines for each class using the invisibility field • Compare resulting 100K extracted lines with 100K DLG lines by subtracting the raster road-density thinned Best Practices (BP) data from the 100K DLG roads (300m grids). 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

9. Iowa Results 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

10. BP and 100K DLG Roads Study area in Iowa DLGs compiled 1981 to 1985 Compiled 2011 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

11. Tom Tomand 100K DLG Roads Study area in Iowa 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

12. Tom TomRoads and Density Strata (class breaks: < 1.5 and more than 1.5 km per sq km) 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

13. Thinning Tom Tom to 100K Radical Law Thinning entire data set Urban Rural Partitions 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

14. Tom TomRoads Thinned to Radical Law 100K 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

15. Atlanta Results 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

16. TomTom Roads and Density Strata (class breaks: < 2.5, 2.5 to 4.5, and more than 4.5 km per sq km) 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

17. Thinning Tom Tom to 100K Radical Law Thinning entire data set Urban Rural Partitions 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

18. Tom TomRoads Thinned to Radical Law 100K 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012

19. Left: All Atlanta TomTom Roads Middle: TomTom Roads thinned using 2 km minimum length Right: TomTom Roads thinned in three density-strata 10 km

20. Summary and Future Work • Density-stratification is a flexible approach to use Thin Network Tool that preserves local density variation better than using a single minimum length • Future work: • Select formal density class breaks for stratifying the country • Identify thinning requirements for 100K and smaller scales • Automate selection of minimum length for each density class • Ensure feature connectivity at density-class boundaries • Test a complete work flow of the Esri transportation generalization tools (include merge divided highway tool, remove road conflicts tool, etc.) [is this necessary to include…] • Test and implement parallel processing to improve performance • Test network navigation capabilities before and after thinning 15th ICA Generalisation Workshop, Istanbul, Turkey, September 13-14, 2012