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u—
Figure 1: NOAA-AVHRR image of a large fire affecting the Mediterranean coast of Spain in 1991. Left, red band;
Right: middle infrared band. Active focii are visible even through a thin cloud layer.
D
—,
=
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hn
which facilitates the discrimination of active
round (figure 1)
e
tion has
been successfully tested in several studies, both at
(
+ . X7 DD : Fp fs de
The use of AVHRR images for fire dete
regional and global scales, espe y over remote
areas where traditional methods are very costly
(Malingreau, 1990; Lan
1992; Kennedy et
al., 1994; Setzer and Pereira
1S, y
1991)
In spite of the potential interest in the use of
AVHRR channel 3 data for fire detection, these
images present several difficulties related to the
I, which was
designed for cloud discrimination and is saturated
at low temperatures (320 K). Consequently, fire
spots can be easily confused with agriculture
burns or even overheated bare soils, which
frequently reach these temperatures during the
summer in the afternoon satellite pass (Belward,
1991). Discrimination from agricultural fires
could be partially achieved by choosing evening
or night images, because this type of burning
tends to be done during periods
(Malingreau, 1990). Monitoring the temporal
dynamism of the target surfaces also provides a
good classification of fire pixels (Lee and Tang,
1990).
low thermal sensitivity of this channe
daylight
Operational use of satellite data in fire detection
in countries with good terrestrial vigilance
requires very high repetitivity. If quick alarms
need to be provided, satellite images should be
received within a range of 15 to 30 minutes of fire
starting. This temporal resolution is only offered
by geostationary satellites, which do not provide
proper spatial resolution for this application.
Therefore, a dedicated mission should be planned
if satellite systems want to be offered as a real
alternative to terrestrial means. A consortium of
European companies funded by ESA and the
European Commission is designing such a system,
named Fuego. This system will provide a 30
minute coverage of high-sensitive middle infrared
data, with spatial resolution in the range of 30 to
120 meters.
4. BURNED LAND MAPPING
One of the main problems affecting fire
management is the lack of appropriate statistics
on burned land. Even the countries more severely
affected by this problem do not have proper data
on fire incidence, as most of the times fires are
not mapped and only general statistics are
available. On the other hand, data are not
available until several weeks (or even months)
after the fire event. As a result, vegetation
recovery is not assessed, and a lack of regrowth
may constitute a severe soil erosion hazard
(Isaacson et al., 1982). Moreover, these field
inventories are often very general. Usually, only
the scorched perimeter is drawn, but no
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 641
