FAQs
Glossary
Reference
Include list of key reference documents: Miller and Thode 2007, Miller et al. 2009, Miller and Quayle 2015.
Caveats
Consider moving this to the Applications section
Fall/winter/early spring fires. Very early or late season fires require special consideration due both to low sun angles and leaf-off conditions of deciduous forests. Typically, RAVG assessments are based on imagery acquired within 45 days of fire containment (“initial assessments”). Imagery acquired between late fall and early spring (depending on latitude) will be affected by low sun angles. In particular, fire effects on north facing slopes are more likely to be hidden due to topographic shadows. As a result, high severity fire effects may be under-represented in these areas. In addition, low to moderate severity in dense stands on east, west, or south aspects may be under-represented due to the low sun illumination angles. Finally, canopy-based metrics are not meaningful for deciduous forests under leaf-off conditions. The current procedure calls for postponing the assessment of fires in this category until the following growing season (“extended assessment).
Mixed cover. It is common for fires to include a variety of cover types, including non-forest cover types. Since RAVG metrics have been calibrated for forest cover, their applicability to other types is limited. It is reasonable to infer that higher values correspond to higher severity in other cover types, but comparisons between various cover types is probably not meaningful.
Change history
RAVG processes and protocols are modified as needed to improve production or products or in response to changes in source data.
- Following the first year of RAVG production (2007), RAVG stakeholders (regional silviculturists, reforestation specialists, remote sensing analysts, and program managers) conducted a technical review and implemented the following changes effective as of the 2008 fire season:
- Summary data for "Grassland / Shrubland / Non Veg" group was expanded from a single value (total acres) to full reporting (acres by ownership/status and burn severity classes).
- The “Non-USFS Wilderness” class was added to the "Ownership / Status" column in RAVG tables. Corresponding symbology was added to RAVG maps.
- Vegetation condition (burn metric) classes were changed from Forested (less than 50% change in basal area) and Deforested (greater than 50%), to four classes (0–25%, 25–50 %, 50–75%, 75–100%). Maps were updated to reflect the same change.
- The "Slope" column was removed from the main RAVG summary table. Slope data are still reported on the raw data tab.