Data Contents

Data Contents

Disclaimer: Some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented without the approval of the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the responsibility of the user.

Availability and Restrictions on Use: Downloadable datasets are available to any user. There are no restrictions on use, except for reasonable and proper acknowledgement of information sources. Those engaged in validating and improving products are encouraged to share revisions with this web site, so the most up-to-date information can be made available. Please contact fsedc@usgs.gov to make updates on product validation.

Spatial Coverage: : Fully developed and subset information is targeted for all National Park Service Units (including Alaska and Hawaii) with recent burns exceeding about 300 acres in size. Landsat data and Delta NBR models, only, are also available as full-scene products, which cover approximately 180x180 kilometers. The latter may be applicable to adjacent lands, if outlying burns occurred at approximately the same time and were fully contained within the Landsat scenes used for assessments. Those digitizing and sub-setting such burns are encouraged to share that information by contacting fsedc@usgs.gov.

Temporal Coverage: The current objective is to analyze all significant NPS burns from fire year 2000 and forward in time. However, earlier burns have been analyzed for research purposes in some cases, and development of recent fire histories on a sustained basis is a future objective for many key parks. When implemented, that would cover the available Landsat 30-meter archive, back to 1982.

Metadata: This ASCII text file follows Federal Geographic Data Committee (FGDC) standards for content and format.

Landsat 30-meter Data: Generally, these binary raster data are delivered through the standard USGS Multi-Resolution Land Characterization (MRLC) processing stream, and accessed via the Image Dates links on the burn information page. They consist of full-scene, terrain-corrected reflectance data for Landsat TM/ETM+ bands 1-5, and 7. The data are scaled to a byte range (0-255), and geo-referenced to the Albers Conical Equal Area projection (see the MRLC web site for further information: http://landcover.usgs.gov/nationallandcover.html). At least two scenes, pre-fire and post-fire, are listed on each burn information page. Some burns, however, may have more than one information page, if both Initial and Extended Assessments were completed; so four or more scenes per burn may be available. In a few cases, burn assessments were derived from Landsat data purchased for research purposes, and will be linked to an archive other than MRLC. They are available at the processing level of the original raw data, and may reflect geographic or radiometric corrections different from MRLC. Users should consult scene header and history files in those cases for specific processing parameters.

Multi-band Geo-Tiff: These are pre- and post-fire Landsat data subset around each burn, and exported in standard Geo-TIFF binary raster format. They are terrain-corrected reflectance data for six Landsat bands (1-5 and 7). They are geo-referenced to the projection and datum used locally by the NPS, typically UTM NAD-27.

Differenced NBR (Delta NBR, DNBR): The NBR difference, pre-fire minus post-fire, is provided in Arc GRID™ format for full-scene and image subsets around each burn. Both are geo-referenced to the projection and datum used locally by the NPS, typically UTM NAD-27 or NAD-83. The DNBR is scaled by 1000, and stored as signed 16-bit data with a potential range of -2000 to +2000. A linear grayscale (black to white) has been applied to the effective range of the data (e.g. -800 to +1100). At least one Delta NBR dataset is offered on each burn information page. Some burns, however, may have more than one information page, if both Initial and Extended Assessments were completed.

Fire Perimeter: Vector data are supplied as ArcView Shape Files™, geo-referenced to the projection and datum used locally by the NPS, typically UTM NAD-27. They represent burn boundaries, including outlying polygons (spot fires), but generally not including interior unburned islands. Polygons are derived from Delta NBR images, using a hybrid of automated and on-screen digitizing methods. This is aided by on-screen overlays of pre- and post-fire false color composites. Generally, points are one-half to one pixel outside apparent burn limits, so polygons are a liberal estimate of burned area, and represent a preliminary interpretation. When needed, questionable burn polygons are identified, which call for further verification from aerial photos or the field. Users are strongly encouraged to review perimeters and report any modifications. As corrections are made, from expert knowledge and/or ground surveys, adjusted perimeters replace previous versions on the website, and validation levels are updated in metadata and status codes.

Severity Thresholds: If stratification of Delta NBR has been completed, usually with the aid of local fire personnel, those results are posted. The values are Delta NBR break points that bracket classes of ecological burn severity; such as enhanced productivity, unburned, low, moderate-low, moderate-high, and high levels. Class names and degree of validation are also provided (see Validation Status, below).

Fire Narrative: When available, this document includes supplemental information provided by the NPS about fire behavior, affected vegetation types, management actions, and other details.

DNBR Acres (nearest 10 acres): Size of total area burned within perimeter(s), as determined from the Differenced NBR burn-severity model. This includes unburned areas that may occur within perimeters, and likely differs from the incident-reported fire size.

Assessment Type: The scenario used to derive the Differenced NBR burn severity model; each conveys slightly different information on fire-effects (see Overview and Methodology):

Initial Assessment - The post-fire scene is acquired as soon after burning as possible. The pre-fire scene generally comes from 1 to 3 years before the fire, during a seasonal period similar to the post-fire scene.
Extended Assessment - The post-fire scene is acquired during the next growing season after fire, usually 6 to 10 months later. The pre-fire scene generally comes from the year of the fire, or 1-2 years before that, during a seasonal period similar to the post-fire scene.
Active Burning - The fire is burning in either the pre-fire or post-fire scene. Active hot spots may be visible and portions of the final burn area may be missing. In other respects, the DNBR could represent either an Initial Assessment or an Extended Assessment.

Validation Status: The following indicate validation levels for Delta NBR and Perimeters. Only checked items apply to deliverables. Items not checked do not apply, or are not yet completed.

Field validation complete (no additional changes to products are anticipated):

An ocular validation has been completed for the Delta NBR.
Validation by field sampling has been completed for the Delta NBR.
An ocular validation has been completed of the fire Perimeter.
Validation by field survey has been completed for the Perimeter.
Validation is based on fieldwork extrapolated from nearby burns in similar ecosystems.
Validation resulted in thresholds for burn severity levels (see Severity Thresholds).
Validation resulted in a revision to the Perimeter, which now replaces the original.

Field Validation Incomplete:

Ocular validation is in progress.
Sampling using the Composite Burn Index has been initiated.
Sampling using some other methodology is underway.

Ocular validation refers to any number of the following: 1) review of aerial photos or other high resolution imagery; 2) spot checks on the ground by vehicle or foot; 3) comparison to other reliable perimeter maps; or 4) expert knowledge from fire staff who are familiar with the burn.

Field sampling and surveys include validation using a statistically valid sampling design and a relatively high degree of locational accuracy. This could include GPS traverses as well as plots or transects, where data collected relates to ecological burn severity. Survey of perimeters consists of acquiring a number of points by GPS along several sections of the burn boundary, particularly where detected burn features are faint. Aerial photo interpretation incorporating photogrammetry may also qualify.