Ecological regions of Idaho	Detail of western Idaho

Details

Name The name of the level IV region Parent region The name of the enclosing level III region Area The area of the level IV region

Options

Transparency Determines how much the underlying layer(s) will show through this layer. Color level IV: color each level IV region with a different random color level III: color each level III region with a different random color none: leave all level IV regions transparent, except for the outline Line color Defines the color used to draw the region outlines

Origin

This data is available directly from the EPA.

Description of data source

Abstract

The approach used to compile this map is based on the premise that ecological regions are hierarchical and can be identified through the analysis of the spatial patterns and the composition of biotic and abiotic phenomena that affect 1987, 1995). These phenomena include geology, physiography, vegetation, climate, characteristic varies from one ecological region to another regardless of the hierarchical level. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I is the coarsest level, dividing North America into 15 ecological regions. Level II divides the continent into 52 III, the continental United States contains 104 ecoregions and the conterminous United States has 84 ecoregions. Level IV is a further subdivision of level III ecoregions.

The level IV ecoregions were compiled at a scale of 1:250,000 and depict revisions and subdivisions of earlier level III ecoregions that were originally compiled at a smaller scale. In this data layer, states where ecoregions have not yet been subdivided to level IV are represented collaborative project primarily between USEPA Regions, USEPA National Health and Environmental Effects Research Laboratory (Corvallis, Oregon), United States Department of Agriculture-Natural Resources Conservation Service (NRCS, the United States Department of Agriculture-Forest Service (USFS), United States Department of the Interior-Geological Survey (USGS)-Earth Resources Observation Systems (EROS) Data Center, and with multiple state environmental and natural resource agencies.

The project is associated with an interagency effort to develop a common framework of ecological regions. Reaching that objective requires recognition of the differences in the conceptual approaches and mapping methodologies applied to develop the most common ecoregion-type frameworks, including those developed by the USFS. As each of these frameworks is further refined, their differences are becoming less discernible. Regional collaborative projects, where some agreement has been reached among multiple resource management agencies, are a step toward attaining consensus and consistency in ecoregion frameworks for the entire nation.

Purpose

Supplemental Information

1) Prior to digitizing, each base map must be initialized to orient the map and relate it in geographic coordinates to the surface of the earth. When the registration tics are entered at the start of digitizing a transformation error of <0.003 must be achieved in order to insure a high level of registration accuracy. The person responsible for digital data entry completes a data sheet describing coverage name, date of entry, and whether a topology for the coverage is established.

2) All level IV ecoregion delineations and most all level III revisions are digitized from the U.S.G.S. 1:250,000 base maps. For this coverage, USECO, the revised level III boundaries have been smoothed and generalized appropriate for a 1:7,500,000 display scale. Prior to digitizing each base map must be initialized to orient the map and relate it in geographic coordinates to the surface of the earth. When the registration tics are entered at the start of digitizing a transformation error of <0.003 must be achieved in order to insure a high level of registration accuracy. The person responsible for digital data entry completes a data sheet describing coverage name, date of entry, and whether a topology for the coverage is established.

3) After each 1:250,000 base map has been digitized, a topology for each coverage is established. This function creates unique identities for each polygon.

4) Next each base map is tested for polygon errors through an internal editing function. Errors are corrected for unlabeled polygons, unclosed polygons, or polygons with more than one label. Topology is reestablished for each coverage and tested again until no error are indicated.

5) The digital coverage is then plotted at the same scale as the original base map. This coverage is overlaid on a light table with the original and visually inspected for replication of original lines with digitized lines. Two individuals independently inspect the coverage for accuracy.