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EPA 40km Hexagons for Conterminous United States

Dates

Publication Date
Time Period
1992

Citation

White, D.,1992, EPA 40km Hexagons for Conterminous United States: U.S. Environmental Protection Agency, https://doi.org/10.5066/P9C56AY1.

Summary

This dataset of 40 square kilometer (sq. km) hexagons was created by the U.S. EPA's Environmental Monitoring and Assessment Program (EMAP) and is being released by the U.S. Geological Survey for public use. The 40 sq. km hexagons were derived from a grid consisting of a triangular array of points that cover the United States and neighboring Canada and Mexico. The base grid of points had a companion areal structure called a tessellation. The base tessellation hexagons constituted this tessellation. In other words, surrounding each grid point was a hexagon that defines the area within which all points are closer to this grid point than to any other, and the set of hexagons defined this way completely and -mutually exclusively covers [...]

Contacts

Attached Files

Click on title to download individual files attached to this item.

EMAPgrid_readme.txt
“Original Read Me file for 40-sq km hexagon sampling grid”
14.01 KB
Overton_etal_1991.PDF
“Original design report on the EMAP sampling grid”
2.29 MB
Spence+White_EMAPgrid_TechRpt_1992.pdf
“Original technical report on the EMAP sampling grid”
135.07 KB
White_2000.pdf
“Global grid using a diamond tessellation for environmental sampling and modeling”
6.34 MB
White_etal_CAGIS_1992.pdf
“A sampling design created to address a wide variety of environmental issues”
2.4 MB
Shapefile: EPA_Hexagons_40km.zip
EPA_Hexagons_40km.dbf 14.5 MB
EPA_Hexagons_40km.prj 484 Bytes
EPA_Hexagons_40km.sbn 2.99 MB
EPA_Hexagons_40km.sbx 161.01 KB
EPA_Hexagons_40km.shp 54.15 MB
EPA_Hexagons_40km.shx 2.58 MB

Purpose

The original hexagon layer was created because hexagons: • Reduce sample bias, and are the closest shape to a circle that can tessellate • Are a preferable shape for connectivity or movement path analysis • Visually break artificial linear patterns, diminish any orientation bias found with square grids • Have less distortion over large distances (curvature of Earth) • Make finding neighbors more straightforward (e.g., hotspot analysis, outlier analysis) The U.S. Fish and Wildlife Service has been using the 40 sq. km hexagon tessellation for a multi-agency project in the Gulf of Mexico, and has received numerous requests for the hexagon layer for other projects and research. Because the layer is no longer available online through the EPA, the USGS and USFWS are releasing the layer so that it may be distributed and accessed by those interested parties.

Map

Spatial Services

ScienceBase WMS

ScienceBase WFS

Communities

  • Patuxent Wildlife Research Center

Tags

Provenance

Additional Information

Identifiers

Type Scheme Key
DOI https://www.sciencebase.gov/vocab/category/item/identifier doi:10.5066/P9C56AY1
USGS_ScienceCenter https://www.sciencebase.gov/vocab/category/item/identifier Patuxent Wildlife Research Center
USGS_MissionArea https://www.sciencebase.gov/vocab/category/item/identifier Ecosystems
USGS_keywords https://www.sciencebase.gov/vocab/category/item/identifier Ecology,Geography,Wildlife Biology

Shapefile Extension

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