The ground sampled plots will be on a systematic hexagonal grid in the annual inventory. There will be at least one ground sampled plot per hexagonal grid area. In both cases, a phase one sample is used for stratification.
Aerial photography is used by placing a grid over the region of interest, i.e. a state.
The grid points are photo interpreted as to whether they are forested or nonforested. The forested plots are further photo interpreted by volume class. Field crews visit a subset of the photo-interpreted plots and record information on the status of the resource. An annual inventory provides current information every year about the resource. However, the cost of an annual inventory is higher than for a periodic inventory.