Stevens, 1997

Stevens, D. L., Jr. 1997. Variable density grid-based sampling designs for continuous spatial populations. Environmetrics 8:167-195.

Many environmental resources, such as mineral resources or vegetation cover, or environmental attributes, such as chemical concentration in a stream or benthic community structure, are most appropriately sampled as continuous populations distributed over space, but most applied sampling theory and
methodology is concerned with ®nite, discrete populations. This paper reports sampling methodology that explicitly recognizes the continuous nature of ecological resources. A family of designs are developed to permit control of the spatial dispersion of the sample, variable spatial density, and nested subsampling. The designs have non-zero joint inclusion probability densities, so that rigorous design-based inference and variance estimation are possible.