Ownership18_2 is derived from CAL FIRE's SRA18_2 dataset, and GreenInfo Network's California Protected Areas Database (CPAD17a).

CAL FIRE tracks lands owned by federal agencies as part of our efforts to maintain fire protection responsibility boundaries, captured as part of our State Responsiblity Areas (SRA) dataset. This effort draws on data provided by various federal agencies including USDA Forest Service, BLM, National Park Service, US Fish and Wildlife Service, and Bureau of Inidan Affairs. Since SRA lands are matched to county parcel data where appropriate, often federal land boundaries are also adjusted to match parcels, and may not always exactly match the source federal data.

Federal lands from the SRA dataset are combined with ownership data for non-federal lands from CPAD, in order to capture lands owned by various state and local agencies, special districts, and conservation organizations. Data from CPAD are imported directly and not adjusted to match parcels or other features. However, CPAD features may be trimmed if they overlap federal lands from the SRA dataset.