Environmental Engineering Reference
In-Depth Information
TABLE 2.4
Uses of Remote Sensing for Environmental and Natural Resource Studies
Information Desired
Applicable Imagery
Regional environmental studies of air, water and vegetation
Satellite imagery
quality, flooding
(a) On a changing or seasonal basis
(a) LANDSAT
(b) High resolution but incomplete global coverage
(b) SPOT, IKONOS, etc.
Surface and groundwater studies (
large to local areas
)
CIR and Satellite (MSS) imagery
(a) General
(a) CIR and MSS imagery
(b) Thermal gradients indicative of pollution or saltwater
(b) Thermal IR scanner (ETM)
intrusion of surface water
(c) Subsurface seepage
(c) Thermal scanner (ETM)
Vegetation
: forestry and crop studies (large to local areas) identify types,
CIR and Satellite (MSS) imagery
differentiate healthy from diseased vegetation
Mineral resource studies
MSS and hyperspectral imagery
(a) Based on landform analysis
(b) Based on plant indicators
The selection of imagery depends upon availability, the study purpose, and the land area
involved. Stereoscopic examination and interpretation of aerial photographs is the basic
analytical method.
Remote-Sensing Imagery and Interpretation
Regional Geologic Studies
On a regional basis, landform is the most important element of interpretation for geotech-
nical studies. In general terms, landform reflects the relative resistance of geologic materi-
als to erosion. Some relationships among landform, rock type, and structure are apparent
on the portion of the physiographic diagram of northern New Jersey in
Figure 2.10.
The
geology of the area is shown in
Figure 2.2.
Landform is also evident in
Figure 2.5,
a false-
color satellite image, and in
Figure 2.6,
a SLAR image.
Millions of years ago the area illustrated in the figures was a peneplain. Modern phys-
iography is the result of differential erosion between strong and weak rocks. Much of the
area has been subject to glaciation (
Section 7.6.1),
and the limit of glaciation (the terminal
moraine) is given on the Geologic Map. The ridges and uplands, apparent on the physio-
graphic diagram and the figures, are underlain by hard rocks resistant to erosion, such as
the conglomerate of the Delaware River Water Gap, the crystalline rocks of the Reading
Prong (primarily gneiss), and the basalt dikes of the Watchung Mountains. Also apparent is
the scarp of the Ramapo Fault, along the contact of the upland gneiss and the Triassic sand-
stones and shales. The folded sedimentary rocks in the northwest portion of the figures
include the conglomerate ridge, but are mostly relatively soft shales, and soluble dolomites
and limestones. The shales and soluble rocks are much less resistant to erosion than the con-
glomerate, gneiss, and basalt. They erode more quickly and, therefore, underlie the valleys.
The Great Valley is mostly underlain by the soluble rocks, i.e., dolomite and limestone.
Farther to the northwest are the essentially horizontal beds of sandstones and shales of the
Pocono Mountains. Their apparently irregular surface has been gouged by the glacier.
Satellite imagery is most important for terrain analysis where detailed geologic maps
are generally not available, such as in parts of Africa, Asia, and South America. Digital
sensors may not provide adequate coverage for areas with frequent cloud cover; radar,
which penetrates clouds, is an option.
