Abstract |
Precision of systematic designs for sampling continuous response variables defined over a continuous spatial region have been extensively investigated. Estimation of variance, particularly for triangular grids, has been given less attention. Two of the designs proposed for sampling environmental resources in the Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) are based on a triangular grid. Implementation of either design requires derivation and evaluation of a variance estimator adequate for the purposes of EMAP. The performance of the proposed variance estimator was assessed under various surface model representations of the continuous response variable. Of the designs examined, a tessellation-stratified design permitted better estimation of variance, and was generally more precise, than a strict systematic design. (Copyright (c) 1993 by Marcel Dekker, Inc.) |