The Full Picture

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The advanced fire information system

Philip Frost and Dr Bob Scholes, South African Advanced Fire Information System

he South African Advanced Fire Information System

(AFIS) is the first near real-time satellite-based fire moni-

toring system in Africa. It was originally developed for,

and funded by, the electrical power utility Eskom, to reduce the

impact of wild fires on regional electricity supply.

Fires under-

neath the 28,000 km of power lines can cause flashovers which

severely affect electricity supply. The loss of life and destruction

of property caused every year by wildfires further emphasised

the need to develop an operational, early warning fire informa-

tion system that could alert the disaster management,

firefighting, farming and forestry communities on the location

and trajectory of blazes, as well as capturing information on the

frequency and distribution of fires for researchers. In 1999 the

Terra polar-orbiting satellite was launched, with Aqua follow-

ing in 2002. Both have a MODIS sensor on board that can detect

fires with high precision four times a day. These data are coupled

with observations from Meteosat Second Generation (MSG), a

geostationary weather satellite that provides slightly coarser and

less sensitive fire location information every 15 minutes. Eskom

implemented AFIS in June 2004, scanning every 15 minutes

within a buffer of 5 km along all transmission lines, searching

for any fire hotspots. With the detection of a fire, e-mail and

SMS text messages are immediately sent to affected parties. AFIS

was first implemented using propriety GIS technology, but has

now been reengineered as an Open Geospatial

Consortium-compliant Sensor Web application

which is currently being developed.

Hotspot detection

AFIS currently relies on contextual algorithms for

hotspot detection using the two MODIS sensors and the

SEVERI sensor aboard the geostationary METEOSAT-8

satellite. Though the SEVERI provides almost near real-

time hotspot detection, it can only resolve large hotspots

(five hectares or more in extent), whereas MODIS can

resolve hotspots less than a hectare in size.

The hotspot detection algorithm was originally devel-

oped for the Advanced Very High Resolution Radiometer

(AVHRR) sensor flown aboard the TIROS satellites. The

algorithm uses the short wave infrared and thermal

bands to discriminate fire pixels from background pixels.

The algorithm first classifies a pixel according to a fixed

threshold, e.g. $T > 310K$, to identify potential fire

pixels, and the remaining pixels are called background

pixels. The neighbourhood of this pixel is then searched

for background pixels, growing the neighbourhood if

necessary to ensure that at least 25 per cent of the neigh-

bourhood pixels are background pixels. From this set

Advanced fire warnings

The MODIS active fires are incorporated into the weather report

once a week on national television

The AFIS web mapper enables people to view fire locations

via the Internet

OCIETAL

ENEFIT

REAS

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ISASTERS