Large-scale applications of remote sensing for the purpose of preparing crop estimates, natural resource inventories, disaster assessments, etc. for a given geographic region will, in general, involve questions of sampling, since complete coverage of the total geographic region and subsequent analysis of data collected with complete coverage appear technically and economically infeasible. This is true regardless of whether an aircraft, or a satellite is involved, and It applies equally to photography, multispectral measurements, radar, etc. Thus, even if remote sensing provided completely accurate data, estimates (of crop acreage, natural resources, extent of disaster, etc.) for the total region under study will be subject to an error, the so-called error of estimate. This error arises due to the fact that inferences based on selected observations within the region are drawn regarding the characteristics of the total region