Collecting Data from a Permanent Grid Sampling Frame via a Mobile Mapping Instrument

The National Agricultural Statistics Service (NASS) conducts the June Area Survey (JAS), which is based on an area frame. Segments of land comprise the sampling units for the JAS. Building and constructing an area frame is expensive and time consuming. The agency is evaluating the use of a permanent grid sampling frame as a cost-saving initiative. The proposed grid frame would include sample units having roughly equal-sized and shaped areas called grid cells. The grid cells would be stratified by agricultural intensity and content and then a stratified random sample drawn. A challenge associated with this proposed approach is that only a portion of an agricultural field may lie within the selected grid cells whereas currently sampled segments have boundaries that follow roads or other physical features. Because of the presence of partial fields, mobile mapping technology may be critical for proper identification of the areas to be included in a sampled grid cell. Using mobile mapping technology would also allow for replacing the aerial photo and paper questionnaires, thus modernizing NASS’s data collection efforts and improving data quality. To test the concept of permanent grid cells in conjunction with the mobile mapping instrument, enumerators (field interviewers) in North Carolina, Pennsylvania and South Dakota visited with farm operators during the summer of 2014. For each sampled grid cell, the enumerators completed an evaluation form to obtain information on a variety of issues including 1) those associated with the grid concept, 2) use of a mobile mapping instrument, 3) connectivity and 4) visualization problems associated with the iPad (e.g. sun glare). This report documents the challenges faced, as well as the lessons learned, from collecting data using grid cells with the mobile mapping prototype and discusses future instrument enhancements.