The Master Sample
a probabilistic sampling approach
NABat monitoring follows a master sample approach in which North America is divided into a series of 10 x 10 km (100 km) grid cell frameworks. The generalized random-tessellation stratified (GRTS) survey design algorithm then assigns a spatially balanced and randomized ordering (GRTS order) to each cell within its respective framework.
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Grid cells are prioritized numerically; the lower the number, the higher the sampling priority. Cells can then be selected for monitoring following the GRTS order, ensuring both randomization and spatial balance. Monitoring within this standardized framework allows statistical inference to non-surveyed locations and ensures the validity of analyses at regional and range-wide scales using data collected by dozens of partners across the continent.
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