Assessing accuracy of net change derived from land cover maps

Net change derived from land-cover maps provides important information for environmental monitoring and modeling. To better target the objectives of net change accuracy, we require modifications of the sampling design and analysis protocols typically implemented for assessments focusing on single date or gross change maps. Mean absolute deviation estimated for user-defined reporting domains is suggested to characterize net change accuracy. Stratified sampling is often desirable to improve precision for high priority estimates (e.g., high net change domains), but decisions regarding the number and identity of strata must be made recognizing the precision trade-offs among the multiple estimates of interest in a net change assessment. The accuracy assessment strategy and a protocol for evaluating sampling design options are demonstrated using a population of map and reference net change derived from existing land-cover maps and representing change from 1990 to 2000.