The wetland status and trends monitoring program is a random sample survey designed to provide an ongoing assessment of the gain and loss of wetland acres in Minnesota. Initiated in the spring of 2006, this project involves the periodic acquisition and interpretation of aerial photography on nearly 5,000 permanent sample plots scattered around the state. Wetland gain and loss is determined by comparing subsequent photos of each sample plot using GIS technology.
Wetland quantity measurements are made using photo-interpretation of high-resolution natural color stereo-imagery for randomly selected 1-square mile plots, known as primary sampling units (PSU). The survey uses a cyclical, interpenetrating panel structure based on the Generalized Random Tessellation Stratified (GRTS) design to ensure that random samples are spatially distributed across the state (Stevens and Olsen 2004). Imagery is acquired, and photo-interpretations are performed for 1830 PSUs each year. Of these, 1580 PSUs are assigned to one of three repeating panels and interpreted every third year and 250 PSUs are interpreted every year.