Strategies for exploiting auxiliary information and achieving spatial balance in environmental surveys

Many schemes have been proposed in literature to achieve “well spread” samples, and some of them can take advantage of auxiliary information. Alternatively, well spread samples can be straightforwardly obtained by means of schemes widely adopted in environmental and ecological surveys, such as one-per-stratum stratified sampling or systematic sampling. In both cases the auxiliary information can be adopted at the estimation level and therefore the comparison of the performances of alternative strategies exploiting auxiliary information at different levels is welcomed.