An Image Analysis System to Develop Area Sampling Frames
for Agricultural Surveys
James J. Cotter
USDA-NASS, Room 4813 South Building, Washington, DC 20250
ABSTRACT: A computer
digitization and some sampling procedures has been developed to create area
frames to collect agricultural data.
The system, known as CASS -
Computer Aided Stratification and Sampling, automates a procedure which reduces
errors and labor costs in the previous manual system. Although material costs
have increased and resolution is a problem, stratification has been enhanced and
data utility increased.
The National Agricultural Statistics Service (NASS) has been developing, using and analyzing area
sampling frames since 1954 as a vehicle for conducting surveys to gather information regarding
cost of production,
grain yield and production,
inventories and other agricultural items (Cotter and Nealon, 1987). An area frame for a land area,
typically a state or county, consists of a collection or listing of all parcels of land for the area of
interest. These land parcels can be delineated based on factors such as ownership or based simply
on easily identifiable boundaries as is done by NASS. Area frames are critical
quality estimates, as they provide complete coverage with all land areas being represented
probability survey with a known (not necessarily equal) chance of selection.
The previous manual procedure used to develop area frames was slower and more labor intensive.
The development of an area frame for a single state on paper-based materials may require 11,000
hours and cost over $150,000.
This paper will briefly describe the materials and procedures used in developing a paper-based
This will then be followed by a description of the new automated procedures
developing area frames using digital inputs, which is now operational.