O Portal de Notcias da Globo The application Amazônia.vc, launched by Globo Television in partnership with the new website Globo Amazônia, makes it possible to view in one same screen the data of two systems used by the Brazilian space research institute to monitor the devastation of the Amazon: the Fire Monitoring and the System of Deforestation Detection in Real Time, known as Deter.
The launch of CBERS 2, in October 2003, on the Chinese Long March 4B rocket (Picture: INPE)
Deter was created as an alert system to support surveillance and
deforestation control. It uses images mainly from sensors called
Modis, aboard the Terra and Aqua satellites, launched by the
National Aeronautics and Space Administration (NASA). Both
satellites are in 705-kilometer orbits, but Terra provides
morning observations and Aqua, afternoon observations, of the
Amazon. Because of lighting conditions, morning images are the
most adequate to Deter.
The system also uses data from WFI, a sensor on
board of the China-Brazil Earth Resources Satellite (CBERS 2).
Modis and WFI have a spatial resolution of 250 meters, which
means that the images they capture cover an area of 900
kilometers by 900 kilometers and have pixels equivalent to a
length of 250 meters by 250 meters.
The satellite images are received by the space
research institute and analyzed visually by a team of six
technicians who record all the deforested points. They map both
shallow cut areas (clearing of all trees) and areas in process
of deforestation because of forest degradation (when only part
of the trees are cut, leaving the forest scarcer).
Loose margin
“Deter works with a looser margin [in terms of classifying what
is deforestation] in order to register the more threatened
areas”, explained Dalton Valeriano, coordinator of the Amazon
Program at INPE.
In the case of shallow cut areas, the government
inspection organs can look for the responsible if the
deforestation is illegal. In the case of areas of progressive
degradation, besides finding the responsible, the State can act
to reverse the process.
Artistic conception of Landsat 5 at space (Picture: NASA).
Deter detects only deforestation areas larger than 25 hectares
(or 2.5 square kilometers) but, due to cloud coverage, not all
of these areas are identified by the system. “In deforestation
areas with more than 2 square kilometers, we have a margin of
success close to 100%”, said Valeriano. He added, however, that
due to government inspections, the deforestation of large areas
is decreasing.
About 25% of the deforestation in the Amazon
happens in areas smaller than 25 hectares, making them invisible
to Deter. Other considerable amount happens in areas of up to 50
hectares, in which Deter has a greater margin of error in
detection. That is why Valeriano estimates that the system is
able to monitor about half of the total deforestation of the Amazon.
Annual Survey
Besides Deter, the institute carries out a more
detailed annual survey of deforestation with the Program for the
Estimation of Deforestation in the Brazilian Amazon, known as
PRODES, that has a precision rate of 95%. Thanks to this
program, we know that the Legal Amazon already lost 728.526
square kilometers of original forest (around 17% of its total).
For its greater level of precision, Prodes is the
most important method to monitor deforestation in the medium and
long term. “Prodes cannot fail because the international
community will think that Brazil is hiding data”, explained
Valeriano.
The system uses images captured by Landsat 5, an
American satellite launched in 1984. Since it has exceeded 20
years of its designed life expectancy, the images it captures
present distortions that impair georeferencing (the
determination of the exact location of the pictured area).
“In April, it broke down”, observed Valeriano. “We
can’t depend on the Landsat. With satellites, having one is like
having none”, he added. To guarantee Prodes’ reliability, the
institute uses complementary images from CBERS 2 and buys some
captured by the DMC system, a constellation of five foreign
satellites.
A team of around 30 technicians analyzes 213
images that cover all the Brazilian Legal Amazon. The first to
be analyzed are the most critical areas such as the “arc of
deforestation”, a large fringe of the Brazilian territory, along
the frontier that separates the North and Central West regions
of the country.
Radiation
The Fire Monitoring happens by tracking the electromagnetic radiation spectrum of the Earth’s surface. This technique is similar to the one used by military satellites in the past to watch the launch of enemies’ missiles. The sensor in the satellite records the radiation of the heat produced by the fire in the forest as it recorded the heat produced by the missile’s launch.
Artistic conception of the Terra satellite (Picture: NASA).
Different from Prodes and Deter, the map of fires is produced
automatically by algorithms rather than technicians. Since the
sunlight reflection in the water mirrors could be erroneously
interpreted as fires, a mask with all the rivers and lakes is
applied over the maps, leaving only the fires detected on land.
The system is updated six times a day with data
from various foreign satellites as Terra, Aqua and the
environmental satellites Goes 10 and Goes 12. The last two are
geostationary, which means they orbit at a speed matching the
Earth’s rotation, at an altitude of approximately 36,000
kilometers, and hover continuously over one fixed position on
the Earth’s surface (Goes 12 is located over the Amazon River).
The INPE maps out fires all over Brazil and
neighbor countries, but in Amazonia.vc, we only use data on the
Brazilian Legal Amazon.
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