Rapid Assessment of Vegetation Condition after Wildfire (RAVG) Basal Area Percent Change (Image Service)

The USDA Forest Service Rapid Assessment of Vegetation Condition after Wildfire (RAVG) program produces geospatial data and maps of post-fire vegetation condition using standardized change detection methods based on Landsat or similar multispectral satellite imagery. RAVG data products characterize vegetation condition within a fire perimeter, and include estimates of percent change in basal area (BA), percent change in canopy cover (CC), and a standardized composite burn index (CBI). Standard thematic products include 7-class percent change in basal area (BA-7), 5-class percent change in canopy cover (CC-5), and 4-class CBI (CBI-4). Contingent upon the availability of suitable imagery, RAVG products are prepared for all wildland fires reported within the conterminous United States (CONUS) that include at least 1000 acres of forested National Forest System (NFS) land (500 acres for Regions 8 and 9 as of 2016). Data for individual fires are typically made available within 45 days after fire containment ("initial assessments"). Late-season fires, however, may be deferred until the following spring or summer ("extended assessments"). National mosaics of each thematic product are prepared annually. The associated burned area perimeters are available via the Enterprise Data Warehouse (EDW, see https://data.fs.usda.gov/geodata/edw/datasets.php). Assessment type (initial or extended assessment) for each fire is included as an attribute in the perimeter dataset.美国农业部林务局（USDA Forest Service）野火后植被状况快速评估（Rapid Assessment of Vegetation Condition after Wildfire, RAVG）项目，采用基于陆地卫星（Landsat）或同类多光谱卫星影像的标准化变化检测方法，生成野火后植被状况的地理空间数据与专题地图。 RAVG数据产品可表征火灾边界内的植被状况，涵盖断面积变化百分比（basal area, BA）、冠层覆盖度变化百分比（canopy cover, CC）以及标准化综合燃烧指数（composite burn index, CBI）的估算值。 标准专题产品包括7级断面积变化百分比（BA-7）、5级冠层覆盖度变化百分比（CC-5）与4级综合燃烧指数（CBI-4）。 根据适配影像的可获取情况，RAVG产品将针对美国本土（conterminous United States, CONUS）内上报的所有野火事件生成，此类事件需至少包含1000英亩国家森林系统（National Forest System, NFS）用地（2016年起第8、9区域调整为500英亩）。 单场火灾的数据通常可在火灾封控后45天内公开，即“初始评估”产品；但季末火灾的相关数据可能推迟至次年春季或夏季发布，即“延期评估”产品。 各专题产品的全国镶嵌图每年编制一次。 相关的火灾边界数据可通过企业数据仓库（Enterprise Data Warehouse, EDW，详见https://data.fs.usda.gov/geodata/edw/datasets.php）获取。 每场火灾的评估类型（初始或延期评估）已作为属性字段纳入火灾边界数据集。