Geology Reference
In-Depth Information
affect the interpretation of the TIR imagery. Vice (2007) observed many of these same effects while using TIR
scanners for geothermal exploration. For example, a light fog can obscure the radiant flux of an area. Awet, marshy
area could give a dark (i.e., cool) signal while a bare, south-facing rock that stands up above the surrounding rock
or loose soil could give a very light (i.e., warm) signal. A taller stand of trees within a forest might give a light
(warm) signal compared to the surrounding forest.
Vice (1980) detected a coal fire as an
during a TIR survey of the Black Diamond area of King
County, Washington, as part of the Burlington Northern geothermal exploration program. A Daedalus model 1230
scanner was used for this survey, which had an IFOVof less than 1milliradian and a temperature sensitivity of 1°C.
The TIR survey was flown at night during November 1977. The high resolution of the 1230 model Daedalus
scanner helped to separate the coal fire from a vegetation anomaly on some nearby hills (Figure 13.1.2).
“
accidental outcome
”
This
coal fire (Figure 13.1.2) occurs on state parks and recreation land near the Green River in
King County, Washington, and is a shallow coal fire on the number 12 seam in the Puget Group (Eocene) (William
Kobol, Manager, Palmer Coking Coal Co., personal communication). Disturbed vegetation and warm soil
temperatures characterize the
“
Burning Field
”
“
”
coal fire. For example, the author observed some ground subsidence,
26.6°C ground temperatures, and numerous blackberry bushes, which normally occur on open or disturbed ground,
while doing some field work in the area about 25 years ago. At the present time, the soil temperatures are 21.1°F
(William Kobol, Manager, Palmer Coking Coal Co., personal communication).
Burning Field
A review by Rathmore and Wright (1993) on the monitoring of the environmental impacts of coal mining briefly
discusses the use of TIR. They note that a sensor altitude of less than 3 km (~9000 ft) and a spatial resolution of less
than 3 m work best for detecting coal fires. Rathmore and Wright (1993) also note that imagery acquired during the
night or early morning works best for detecting the coal fires because of the greater thermal contrast.
A report by Kim and Chaiken (1993) on coal fires in abandoned mines and culm banks suggests that attempts to
use TIR for locating the fires had not been successful, although they did not cite any reports. However, Bureau of
Mines personnel were involved in some of the earlier studies (Greene et al., 1969; Dierks et al., 1971). Therefore,
this suggestion may be based on the earlier studies.
The above literature suggests that TIR imagery works best for locating shallow or medium depth coal fires (Greene
et al., 1969; Dierks et al., 1971). Studies by Ellyett and Fleming (1974), Miller and Watson (1980), and Rathmore and
Wright (1993) note that a number of operational factors, i.e., time of day, surface metrological conditions, physical
properties of the ground materials, and topographic conditions, can affect the interpretation of the TIR imagery. The
Green River
Figure 13.1.2. TIR image of the
coal fire, King County, Washington (white oval). The image was
part of a Burlington Northern Railroad survey flown in the fall of 1976 by Intera, a consulting firm in Calgary,
Alberta, Canada. The instrument used for the image was a Daedalus 1210 model thermal line scanner, with an
8
“
Burning Field
”
-
14
m detector, mounted in a light aircraft and flown at an altitude of ~1524
-
1829m (5000
-
6000 ft) above
μ
ground level. Scale is 1:16 000.
