Geoscience Reference
In-Depth Information
This chapter considers key characteristics of spatial designs that serve
these inferential purposes. It introduces some general-purpose sampling
algorithms particularly suited for ecological monitoring that allow, when
properly implemented, inferences to all parts of a defined study area.
Although not exhaustive, the designs discussed here are appropriate and
useful for a wide range of real-world, large-scale, long-term monitoring stud-
ies, as well as real-world, small-scale, or short-term studies. These designs,
when combined and implemented at two or more nested levels, provide a
great deal of flexibility.
The chapter is organized as follows: First, to provide background and con-
text, a general discussion of design characteristics is given. In particular, the
differences between scientific and nonscientific survey designs, as well as
the differences between research and monitoring studies, are discussed. The
differences between research and monitoring studies lead to sets of spatial
sampling designs that are typically more appropriate for one type of study
or the other. Next, spatial sampling algorithms appropriate for each type of
study are described in separate sections, followed by some final comments
and a summary.
Because the spatial design is concerned with geographic space, the termi-
nology surrounding spatial designs is slightly different than classical finite-
population sampling. Translation of a few classical finite-population terms
is provided in Table 10.1.
TABLE 10.1
Traditional Finite-Population Sampling Terms and Their Equivalent Spatial
Design Terms
Traditional Finite-Population Terms
Spatial Design Terms
Term
Definition
Term
Definition
Sample unit
The smallest entity on which
data will be collected
Sample site
A special case of sample unit
that is tied to a geographic
location; can be a point or a
polygon
Population
A collection of sample units
about which inference is
sought
Study area
A collection of sample sites
about which inference is
sought; generally, a polygon
or collection of polygons
Sample
A subset of sample units in
the population
Spatial
sample
A subset of sample sites in the
study area; generally, a set of
points or polygons in the
study area; if polygons, the
sum of their areas is
necessarily less than total
size of the study area
