Understanding Statistics

NASS Surveys: The Foundation of Estimates - Area Frame Samples

In area frame sampling, NASS relies on satellite imagery, aerial photos, and maps to divide the U.S. land area into small segments. Each segment is about 1 square mile, and each has unique and identifiable boundaries outlined on aerial photographs or maps. An area frame sample is a random selection of these segments drawn onto aerial photos. Field investigators called enumerators visit the segments and record information about agricultural activity within the segment boundaries.

The area frame technique can be used to collect information about crops, operator households, animals, grain storage facilities, environmental factors, and so on.

In most States, the segments in the area frame are classified for sampling purposes into four broad categories: land intensively cultivated for crops; land used primarily for livestock production; residential and business areas in cities and towns; and areas devoted to parks, military installations, and other uses.

The area frame sample provides continuous coverage of all agricultural activity in the United States, regardless of changes in farm boundaries and management. This sampling technique guards against omission or duplication in the statistics.

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Last Modified: 01/26/2018