Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 59

FIGURE 3.3 Cross-sectional map of the profile of regolith in field 12a. Units
at the bottom of the map are meters.
both the transect and detailed sampling plan. It can help in determining where a
contaminant may have moved and thus where more samples need to be taken. Such a
map may be developed from data in the soil survey of the field, which is discussed below.
Another useful type of map is the topographical or topo map of the area. An example
of a topo map is given in Figure 3.4. The topo map has lines of equal altitude drawn on it.
They thus show slopes, escarpments, and other important features of a landscape. They
also show which direction water will flow in and where erosion is most likely. In many
cases topological characteristics will need to be taken into consideration when sampling.
For many areas the United States Geological Survey and other government entities
have digital orthophoto quarter quadrangles (DOQQ) photographs or maps of areas of
interest. These are digital photographs that are placed on the Universal Transverse
Mercator Projection (UTM) on the North American Datum (NAD-27). There is also a
NAD-83, and others, that can be used. Digital orthophoto quarter quadrangles have a
ground resolution of 1 meter and cover an area of 3.75 minutes latitude by 3.75 minutes
longitude. It is useful to note that both UTM and NAD-27 are used by GPS units, and
since they are digital, they are compatible with