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Remote Sensing (RS)
Remote sensing involves the use of instruments or sensors to
"capture" the spectral and spatial relations of objects and materials
observable at a distance — typically from above them, e.g., via aerial
photography (e.g., cameras carried on aeroplanes) and satellite imagery.
Remotely sensed data is widely used in fields such as meteorology, minerals
exploration and natural resources management.
Formal Definitions of Remote Sensing
[From NASA
Remote Sensing Tutorial (US)]
"The acquisition and measurement of data/information on
some property(ies) of a phenomenon, object, or material by a recording device
not in physical, intimate contact with the feature(s) under surveillance;
techniques involve amassing knowledge pertinent to environments by measuring
force fields, electromagnetic radiation, or acoustic energy employing cameras,
radiometers and scanners, lasers, radio frequency receivers, radar systems,
sonar, thermal devices, seismographs, magnetometers, gravimeters,
scintillometers, and other instruments."
"Remote Sensing is detecting and measuring of
electromagnetic energy (usually photons) emanating from distant objects made of
various materials, so that we can identify and categorise these objects by class
or type, substance, and spatial distribution."
Remote Sensing in Health Sciences
In 1970, in an article titled "New eyes for
epidemiologists: aerial photography and other remote sensing techniques",
Cline recognised that remote sensing could also have applications in detecting
and monitoring disease outbreaks (Am J Epidemiol 1970 Aug;92(2):85-9).
The
Centre
for Health Applications of Aerospace Related Technologies (CHAART) is part
of the Ecosystem Science and Technology (ECOSAT) Branch of the Earth Science
Division at the NASA Ames Research Centre (US). Since 1985, CHAART has
undertaken a number of projects involving the application of remote sensing and
geographic information systems technology to human health problems, including
the following studies:
- Spatial
patterns of filariasis in the Nile Delta, Egypt and prediction of villages
at risk for filariasis transmission in the Nile Delta: During
1995, NASA sponsored RS/GIS training at CHAART for Dr. Ali Nasser Hassan,
from Ain Shams University, Cairo, Egypt. Dr. Hassan's goal was to use RS and
GIS to explore the spatial patterns of filariasis cases in the Nile Delta.
This disease is transmitted by the mosquito Culex pipiens, which is
frequently found in houses with cesspits in areas with a high water table.
Landsat Thematic Mapper data, which coincided with Dr. Hassan's
epidemiologic field data, were converted into vegetation and moisture
indices, as well as classified into landcover types. Statistical analyses
were used to compare these landcover variables with the spatial distribution
of microfilaria in 201 villages, spread throughout 10 communities. Dr.
Hassan published his results in two papers (see references below);
Dr. Hassan (right) collecting larval Culex pipiens samples in the Nile
Delta
Malaria
in Chiapas, Mexico - The field research focused on the relationship of Anopheles
albimanus mosquito to environmental variables associated with regional
landscape elements, including larval habitats, bloodmeal sources, and resting
sites. The results indicated the importance of flooded pastures and
transitional wetlands for larval habitat, cattle in pastures for bloodmeal
sources, and trees for potential resting sites. The remote sensing research
involved identifying and mapping these landscape elements, along with seven
others, using multitemporal Landsat Thematic Mapper (TM) data. Left:
Landsat TM images of Mexico Coastal Plain from July 1991 showing the wet
season, and the landscape is mostly green. Right: Landsat TM images of
the same Mexico Coastal Plain from March 1992. In the spring season, much of
this area is dry and is purple in this image (right). Some crops are
irrigated, such as banana, but most of the croplands are dry. NASA aircraft
imagery was used to create a map of human settlements, from which 40 villages
were randomly selected for the purpose of this study to examine the
relationship between landscape elements and mosquito-human contact risk (i.e.,
malaria risk). A geographic information system (GIS) was used to calculate the
proportion of each landscape element within a 1-km buffer surrounding each
village. This 1-km radius was based on the typical flight range of an adult Anopheles
albimanus mosquito; within this flight range, it must find bloodmeals,
resting sites, and larval habitat in order to reproduce and transmit malaria.
MALSAT
Malaria is one
of the world's most prevalent diseases, with a world-wide incidence rate of
300-500 million clinical cases annually. Tropical Africa accounts for more than
90% of the total malaria incidence and the great majority of malaria deaths. For
example, in portions of East Africa, especially Kenya, malaria kills between 1.5
and 2.7 million people a year, most of them during the six-month rainy (wet)
season. MALSAT
— Environmental Information Systems for Malaria consists of a small group
of researchers, based at the Liverpool School of Tropical Medicine, UK, who are
investigating the 'Eco-epidemiology' of vector-borne diseases using GIS and
remote sensing techniques. They have published extensively on the ecology of
malaria in sub-Saharan Africa.
You may download the entire MALSAT (Environmental Information
Systems for Malaria, Liverpool School of Tropical Medicine, UK) Web site (images
and text) for offline viewing.
References:
- Hall W. Just Another Medical Geography Page (Web site). URI:
http://www.geocities.com/Tokyo/Flats/7335/medical_geography.htm
(accessed 6 December 2000)
-
Hassan AN, Beck LR and Dister S. Prediction of villages
at risk for filariasis transmission in the Nile Delta using remote sensing
and geographic information system technologies. J. Egypt. Soc. Parasitol.
1998;28(1):75-87
-
Hassan AN, Beck LR and Dister S. Spatial analysis of
lymphatic filariasis distribution in the Nile Delta in relation to some
environmental variables using geographic information system technology. J.
Egypt. Soc. Parasitol. 1998;28(1):119-131
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