Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 77

less expensive. If taking a sample from close to a previously sampled site is sufficient,
postsampling DGPS is sufficient. With this capability sampling sites can be determined
with exceptional accuracy.
Global positioning systems and equipment are constantly being upgraded and
improved, thus when deciding on a GPS receiving unit to use, all the latest advancements
in this technology should be investigated, along with best estimates of where the
technology will be in the foreseeable future.
3.15.2. Ground-Penetrating Radar
Ground-penetrating radar is called for when the field history indicates that something
might be buried in the field or when the field has been traversed by armed forces. The
field history is particularly important in determining if something dangerous, such as
explosives, might be buried in the area. Ground-penetrating radar is also indicated if there
is a likelihood that there are buried tanks, cables, pipelines, or drainage tiles. A hole 1
meter in diameter and 1½ meter deep was found in a field in which a drainage tile had
broken and soil had been washed in. (Such a situation is called a blowout, even though
soil has been eroded into the tile.) This type of field condition can be hard to see until one
is nearly in it. It is thus extremely dangerous for personnel and equipment. Ground-
penetrating radar can show where such blowouts are developing. It can also tell where
drainage tiles are so that they can be avoided during sampling.
Ground-penetrating radar could also be used if the area is suspected of being an
abandoned village or city [13]. In this case it would help determine areas under which
tunnels and caves are located, and thus needs special attention when sampling. Tunnels
and caves can collapse during sampling and trap and even kill personnel, and they thus
represent a hazard to sampling personnel and equipment.
3.15.3. Remote Sensing
Remote sensing in the sense of pictures taken from airplanes or satellites can be valuable
in locating underground features. These are often visible as differences in either the type
or the growth of vegetation. Such pictures can help to determine the sampling pattern that
will be the most useful in a particular field. It can also be useful in showing the
differences in the field before and after the sampling and remediation activities [14].
There is a great wealth of remote sensing information available from the U.S.
government. Much of this comes from NASA's Earth Observing System (EOS). There is
also an Earth Resources Observation Systems (EROS) data center, which specializes in
land processes. Other areas of the environment are covered by other organizations. All
these organizations and their data are brought together in the Distributed Active Archive
Center (DAAC). Much of this information is free or available at a nominal cost [14-17].
3.15.4. GIS
Will a GIS system be used and how will it be used? It is a powerful system that can be
very helpful in relating data from different sources. Water movement through soil