Implementing a land cover stratification on-the-fly

Stratified estimation is used by the Forest Inventory and Analysis program of the USDA Forest Service to increase the precision of county-level inventory estimates. Stratified estimation requires that plots be assigned to strata and that proportions of land area in each strata be determined. Classified satellite imagery has been found to be an efficient and effective means of accomplishing both tasks. This study investigated methods for making the county stratifications available for use with user-defined areas without storing the entire pixel-level stratification and processing it separately for each application. Summaries of stratifications at spatial scales of 6,000 acres and less produced stratified estimates at county level and for user-defined areas ranging in size from approximately 300 square miles to approximately 8,000 square miles that were very similar to stratified estimates obtained using the underlying pixel-level stratifications.