WVLC.FRAG81 - West Virginia Forest Fragmentation at 590 hectare Scale

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: Kurt Riitters, U.S. Forest Service
Publication_Date: 2000
Title:
WVLC.FRAG81 - West Virginia Forest Fragmentation at 590 hectare Scale
Edition: 2
Geospatial_Data_Presentation_Form: Map
Publication_Information:
Publication_Place: Research Triangle Park, NC
Publisher: U.S. Forest Service
Online_Linkage: <URL:http://www.wvgis.wvu.edu>

Description:
Abstract:
This dataset is a grid map for West Virginia at 30 meter Resolution. Each pixel value represents an index of forest fragmentation for the surrounding 590.49 ha.(81x81 pixel) analysis window. The dataset was created by applying a spatial filter to a published map of land cover from the Multi-Resolution Land Characteristics (MRLC) Consortium. The spatial filter computed an index of forest fragmentation from the attribute adjacency table of forest and non-forest land cover types. The [0,1] continuous index was discretized, and a byte representation [1,255] was stored at the center location (i.e., at the center pixel) in a new map. Each pixel in the new map is an index of forest fragmentation, for the surrounding 590.49 ha window, for the corresponding pixel in the original land cover map.

Purpose:
These data were created as part of a national analysis of land cover pattern. A series of derived maps (different indices, different window sizes) is available. They are proposed for consideration by landscape analysts, as independent variables (e.g., covariates, stratification rules), and as "context" information for finer-scale investigations, for example field plots.

Caveats include: Maps in this series are naturally correlated since all came from one map. No warranty or claim is made of the utility of this map for any particular purpose, this is considered to be a research dataset. The forest fragmentation map portrays relative fragmentation, at one scale, considering only forest and non-forest cover types.

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1988
Ending_Date: 1993
Currentness_Reference: Dates of satellite imagery.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: Irregular
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -84
East_Bounding_Coordinate: -76
North_Bounding_Coordinate: 41
South_Bounding_Coordinate: 36
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: pattern
Theme_Keyword: landcover
Theme_Keyword: landscape
Theme_Keyword: forest
Theme_Keyword: fragmentation
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: WV
Place_Keyword: United States
Place_Keyword: West Virginia
Access_Constraints: None
Use_Constraints:
None. Acknowlegement of the U.S. Forest Service would be appreciated in products derived from these data. To support further development of the database, please send a postcard or reprint.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Kurt Riitters
Contact_Organization: U.S. Forest Service
Contact_Address:
Address_Type: mailing address
Address:
Box 12254 3041 Cornwallis Road
City: Research Triangle Park
State_or_Province: NC
Postal_Code: 27709
Contact_Voice_Telephone: 919-549-4015
Contact_Electronic_Mail_Address: kriitters@fs.fed.us
Data_Set_Credit:
The basic data from which this map was derived were provided by the Multi-Resolution Land Characteristics Consortium, hosted by the EROS Data Center.
Native_Data_Set_Environment:
These data are stored as a binary image in band-sequential (bsq) format, row-major order, where each byte is one index value. The image is compressed by using gzip.
Cross_Reference:
Citation_Information:
Originator: Riitters, K.H., O'Neill, R.V., and Jones, K. B.
Publication_Date: 1997
Title:
Assessing habitat suitability at multiple scales: a landscape-level approach
Series_Information:
Series_Name: Biological Conservation
Issue_Identification: Volume 81, pages 191-202.
Other_Citation_Details:
Illustration of computer algorithms and an application.

Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The fragmentation index is based on a proportion derived from the attribute adjacency table of forest and non-forest pixels (see: Process_Step sections). A statistical rule of thumb is that 50 observations are needed to estimate a proportion. The 81x81 pixel analysis window has up to 12960 defined adjacencies (only those involving at least one `forest' pixel, and no "missing" pixels) are used in the calculation). This index is one of several which could have been used instead, and standard textbooks discuss relative strengths and weaknesses. Like other indices, this index is best interpreted as a relative value, in comparison to other pixels on the same map. Comparisons with other maps prepared from different data sources or at different scale are tenuous.
Logical_Consistency_Report:
All cell values are in the range [0,255]. A missing value code (0), was assigned to water or ice land cover types (on the MRLC land cover map), or which were outside the the extent of the MRLC land cover map.
Completeness_Report:
Every non-null cell in the original land cover map has either a non-zero byte value representing the index, or a missing data value.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
The positional accuracy of the derived map is the same as the positional accuracy of the input map.
Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey EROS Data Center
Publication_Date: 2000
Title:
National Land Cover Data West Virginia Version 03-20-00
Type_of_Source_Media: online
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1988
Ending_Date: 1993
Source_Currentness_Reference: Dates of satellite imagery.
Source_Citation_Abbreviation: MRLC
Source_Contribution: Land cover map
Process_Step:
Process_Description:
Derivation of forest fragmentation from land cover:

Land cover data (MRLC) was obtained from EROS Data Center in binary format.

The image was subdivided into sixteen (16) overlapping rectangles using an in-house software tool named SPLITTER.C. The rectangles overlapped to avoid artifacts near image boundaries during the spatial filtering operations.

Each of the rectangles was then processed via spatial filtering to estimate the index as described below. The spatial filtering program is an in-house software tool named SPATCONV.C (Riitters et al. 1997)

After spatial filtering, a map of index values was constructed by reassembling the 16 rectangles into a single image (via an in-house software tool named LUMPER.C, which removed the overlapping parts of rectangles).

The "header file" information for the derived map is as follows. This information is needed for some image import filters. Ulxmap and Ulymap refer to the center of the upper-left pixel. nrows 13240 ncols 13265 nbands 1 nbits 8 layout bsq skipbytes 0 ulxmap 1154670.000000 ulymap 2064600.000000 xdim 30.000000 ydim 30.000000

Spatial filtering proceeded as follows.

Pixels were re-classified into forest and non-forest classes by using the following scheme:

Original MRLC class Forest/non-forest class 11: open water missing 12: perennial ice/snow missing 21: low intensity developed non-forest 22: high intensity residential non-forest 23: high intensity commercial/industrial non-forest 31: bare rock/sand/clay non-forest 32: quarries/strip mines/gravel pits non-forest 33: transitional barren non-forest 41: deciduous forest forest 42: evergreen forest forest 43: mixed forest forest 51: deciduous shrubland forest 52: evergreen shrubland forest 53: mixed shrubland forest 61: planted/cultivated (orchards, vineyards, groves) non-forest 71: grassland/herbaceous non-forest 81: hay/pasture non-forest 82: row crops non-forest 83: small grains non-forest 84: bare soil non-forest 85: other grass (lawns, city parks, golf courses) non-forest 91: woody wetland forest 92: emergent herbaceous wetland non-forest

A 590.49 ha (81x81 pixel) quadrat was centered on each pixel of the original land cover map. An attribute adjacency table was then tabulated, considering only pixel pairs in cardinal directions (i.e., four neighbors per pixel), and counting each pixel pair once. The fragmentation index was then computed from the attribute adjacency table as the frequency of forest-forest pairs, divided by the sum of frequencies of forest-forest plus forest-nonforest pairs. This yields a value of 0 when no forest pixels are adjacent to another forest pixel, and a value of 1 when all forest pixels are adjacent in all cardinal directions to other forest pixels. Thus, the range is from zero (high forest fragmentation)to one (low forest fragmentation). The index is not independent of the amount of forest present in the window. If the center pixel was "missing" in the land cover map, then the index was assigned a "missing" value. Note that the index is defined for all other land cover types.

The calculated values were discretized to the range [1,255] and stored at 30-meter spatial resolution. Thus, a pixel value in the new map represents the index for the surrounding 590.49 ha in the original land cover map.

The transformation used to discretize the values was: D = ( C * 254 ) + 1 where D = discretized value in range [1,255] C = calculated value in range [0,1] If needed, the original calculated values can be approximated by applying the backtransformation: C = ( D - 1 ) / 254 The backtransformed values will be in steps of size approximately 0.00394 as a result of the discretization process.

Source_Used_Citation_Abbreviation: MRLC
Source_Produced_Citation_Abbreviation: WVLC.FRAG81
Process_Date: 1999

Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Grid Cell
Row_Count: 13240
Column_Count: 13265

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Albers Conical Equal Area
Albers_Conical_Equal_Area:
Standard_Parallel: 29 30 0
Standard_Parallel: 45 30 0
Longitude_of_Central_Meridian: -96 0 0
Latitude_of_Projection_Origin: 23 0 0
False_Easting: 0.0
False_Northing: 0.0
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: Row and column
Coordinate_Representation:
Abscissa_Resolution: 30
Ordinate_Resolution: 30
Planar_Distance_Units: meters

Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: WVLC.FRAG81 grid cell.
Entity_Type_Definition: Any of the data elements.
Entity_Type_Definition_Source: U.S. Forest Service
Attribute:
Attribute_Label: Grid cell value.
Attribute_Definition:
Byte value representation of forest fragmentation index.
Attribute_Definition_Source: U.S. Forest Service
Attribute_Domain_Values:
Range_Domain:
Range_Domain_Maximum: 255 (integer)
Range_Domain_Minimum: 0 (integer)

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Kurt Riitters
Contact_Organization: U.S. Forest Service
Contact_Address:
Address_Type: mailing address
Address:
Box 12254 3041 Cornwallis Road
City: Research Triangle Park
State_or_Province: NC
Postal_Code: 27709
Contact_Voice_Telephone: 919-549-4015
Contact_Electronic_Mail_Address: kriitters@fs.fed.us
Distribution_Liability:
Although these data have been processed successfully on a computer system at the U.S. Forest Service, no warranty expressed or implied is made by the USFS regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty.

Metadata_Reference_Information:
Metadata_Date: 20000830
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Kurt Riitters
Contact_Organization: U.S. Forest Service
Contact_Address:
Address_Type: mailing address
Address:
Box 12254 3041 Cornwallis Road
City: Research Triangle Park
State_or_Province: NC
Postal_Code: 27709
Contact_Voice_Telephone: 919-549-4015
Contact_Electronic_Mail_Address: kriitters@fs.fed.us
Metadata_Standard_Name:
FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Security_Information:
Metadata_Security_Classification_System: None
Metadata_Security_Classification: Unclassified
Metadata_Security_Handling_Description: None

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