The BAER imagery support program provides burn severity products deirectly to BAER teams in aid in the development of the final soil burn severity created as part of the emergency BAER assessment.
Scope
Analysts from the USDA Forest Service GTAC and the USGS EROS center provide burn severity products as requested by BAER teams. Products are typically delivered within hours of receiving useable post-fire satellite imagery.
Process
Analysts will monitor satellite imagery to find appropriate pre-fire and post-fire image pairs for applying a change detection analysis typically based on the NBR index. The objective is to provide a rapid delivery of satellite imagery, BARC data, and related geospatial data to USDA Forest Service and Department of the Interior (DOI) BAER teams. The BARC is a thematic map that helps the BAER team prioritize its field work and serves as the primary input to the final soil burn severity map produced by the BAER team. The BAER imagery support program relies primarily on imagery from Landsat sensors (OLI on Landsat 8 and 9 and, previously, ETM+ on Landsat 7 and TM on Landsat 5) and from the European Space Agency's Sentinel-2 MSI. Other multi-spectral sensors can be used provided they have sufficient resolution and the necessary spectral bands. The preferred bands are the near infrared (NIR) and short-wave infrared (SWIR, around 2.2 micrometers), which are ideal for detecting the change from healthy green vegetation to dead vegetation, bare soil and ash. The two bands are used to calculate two indices: the NBR (one for each image) and the dNBR (the change in NBR from the pre-fire and post-fire image). The analyst will rescale the dNBR to an 8-bit integer dataset called the BARC256 since it contains 256 unique values. These thresholds can be roughly related back to original dNBR values by multiplying by 5 and then subtracting 275 (for example, a BARC256 value of 100 would relate to a dNBR value of 225). Lower values in the BARC256 represents unburned areas or lower burn severities and higher values will represent areas that burned with moderate or high severity. The analyst will use their knowledge in remote sensing to determine appropriate thresholds between these values that represent four distinct burn severity classes: unburned to very low severity, low severity, moderate severity, and high severity.
Products
BARC products delivered to BAER teams include the following for each wildfire:
- Geospatial Products, including imagery and derived data
- Satellite reflectance imagery (Landsat, Sentinel-2, or similar)
- Pre-fire scene (spatial subset)
- Post-fire scene (spatial subset)
- Normalized burn ratio and related indices
- Burn severity dataset
- Classified Burned Area Reflectance Classification (BARC4)
- Satellite reflectance imagery (Landsat, Sentinel-2, or similar)
- Ancillary data
- Burned Area Boundary (shapefile)
- Masked areas, if any (shapefile)
- Metadata (text)
- User-friendly visualizations
- Google Earth map (KMZ) with BARC4, imagery, and burned area boundary
Products posted on the BAER imagery Support website:
- Preliminary geospatial products, including imagery and derived data
- Satellite reflectance imagery (Landsat, Sentinel-2, or similar)
- Pre-fire scene (spatial subset)
- Post-fire scene (spatial subset)
- Thumbnail image of post-fire scene
- Normalized burn ratio
- Satellite reflectance imagery (Landsat, Sentinel-2, or similar)
- Final Soil Burn Severity
- Soil burn severity data
- Metadata
- Thumbnail image of soil burn severity data
Applications
The BAER imagery support program provides critical data directly to BAER teams. The delivered BARC products are an intermediate data product used by the BAER teams to help focus their field work and derive a final soil burn severity dataset. The final soil burn severity data is used by the BAER team to assess the need for and application of emergency soil stabilization treatments following a wildfire