A Calibration Experiment in a Longitudinal Survey With Errors-in-Variables

Abstract

The National Resources Inventory (NRI) is a large-scale longitudinal survey conducted to assess trends and conditions of nonfederal land. A key NRI estimate is year-to-year change in acres of developed land, where developed land includes roads and urban areas. In 2003, a digital data collection procedure was implemented replacing a map overlay. Data from an NRI calibration experiment are used to estimate the relationship between data collected under the old and new protocols. A measurement error model is postulated for the relationship, where duplicate measurements are used to estimate the error variance of the new procedure. If any significant discrepancy is detected between new and old measures, some parameters that govern the algorithm for the new protocol can be changed to alter the relationship. Parameters were initially calibrated so overall averages nearly match for the new and old protocols. Analyses on the data after initial parameter calibration suggest that a line with an intercept of 0 and a slope of 1 is an acceptable representation for the relationship between the two determinations. Estimation of the measurement error variances as functions of the proportion of developed land are also given.