The mapping study area was divided into two areas of Modoc and Lassen Counties. The Applegate area consists of approximately 84,574 acres, and work was performed on the project between 2017 and 2021. The Eagle Lake area, consists of approximately 66,402 acres in Lassen County, and Work was performed on the project between 2019 and 2021. The eastern portion of the Applegate area used the 2016 NAIP imagery as a base and the Eagle Lake and western portion of Applegate area were mapped using the 2018 NAIP imagery.

The vegetation classification follows protocols compliant with the Federal Geographic Data Committee (FGDC) and National Vegetation Classification Standards (NVCS). The classification is based on new surveys and classification work conducted in collaboration with CDFW VegCAMP. The map was produced applying heads-up digitizing techniques using a base of one-meter National Agricultural Imagery Program (NAIP) imagery (true-color and color infrared), in conjunction with ancillary data and imagery sources. Map polygons are assessed for Vegetation Type, Percent Cover, Exotics, Development Disturbance, and other attributes. The minimum mapping unit (MMU) is 1 acre; exceptions are made for wetlands and riparian types, which were mapped to a 1/4 acre MMU.

Field reconnaissance and accuracy assessment enhanced map quality. There were a total of 91 classes mapped in the Applegate area. The overall Fuzzy Accuracy Assessment ratings for the final vegetation map at the Alliance level were 92.2 percent at the 60-100% Correct or Acceptable level, and 86.4 percent at the 80-100% Correct or Acceptable level. At the Association level, the Fuzzy Accuracy Assessment ratings were was 88.1 percent at the 60-100% Correct or Acceptable level, and 79.1 percent at the 80-100% Correct or Acceptable level. For the Eagle Lake area, there were a total of 78 mapping classes. The overall Fuzzy Accuracy Assessment ratings for the final vegetation map at the Alliance level were 86.3 percent at the 60-100% Correct or Acceptable level, and 81.9 percent at the 80-100% Correct or Acceptable level. At the Association level, the Fuzzy Accuracy Assessment ratings were was 84.0 percent at the 60-100% Correct or Acceptable level, and 72.4 percent at the 80-100% Correct or Acceptable level. See the contingency tables (https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=192229) for more detailed information.