Agricultural Aircraft Offer a Different View of Remote Sensing
Agricultural engineer Steven
Thomson (lower left) and
engineering technician Roger
Bright (lower right) check
installation of a camera
system mounted on an
agricultural aircraft as
ARS pilot David Poythress
checks the video monitors
in the cockpit.
Sometimes the solution to a problem is in one's own backyard. For agricultural
engineer Steven J. Thomson, readily available agricultural airplanes
provided a solution to the need for high-resolution images as part of
remote sensing techniques for the Mississippi Delta.
Thomson, located in the ARS Application
and Production Technology Research Unit in Stoneville, Mississippi,
is applying remote sensing technology using agricultural aircraft to
projects as diverse as managing crop water stress, controlling invasive
imported fire ants, and producing catfish.
"Remote sensing has opened a new window on our understanding of the Earth, its climate and natural resources, and the effects of our activities over the past 30 years," says Mark A. Weltz, ARS national program leader for watershed and remote sensing research. "But we're still learning how to extract the vast amount of information that's available and apply it to agricultural systems in cost-effective ways."
Pilot David Poythress activates
the cameras located in the belly
of an agricultural aircraft with
a remote control strapped to
his leg. ARS engineers also
installed a video monitor in
the cockpit to orient the
pilot over the field.
Thomson first developed the method to collect field images as part
of a practice known as precision agriculture. The idea is to determine
which areas of a field require more attention by growers of cotton,
soybeans, corn, and other crops. This helps growers save on input costs,
such as fertilizer and pesticide, and reduces the amount of pollutants
that could potentially run off into the environment.
Thomson would like to use this system as a substitute for, or to supplement
images obtained by, general aviation aircraft.
"An advantage of agricultural aircraft is that they're much easier to schedule for frequent remote sensing because they're used in the field for spray operations anyway. The imaging system essentially gets a free ride. The setup includes an ergonomic control to allow for easy operation by the pilot with minimal distraction." A slide-mounted box, approved by the Federal Aviation Administration, houses the camera, he says.
An infrared image can distinguish
weeds from cotton. Technician
Roger Bright (seated) and agricultural
engineer Steven Thomson compare
the infrared image to a standard
photo (right monitor).
The new system is being studied for several applications, such as detecting
weeds in cotton and soybean fields using digital video and spotting
nutrient or water stress in crops using thermal imaging.
The researchers configured and mounted standard digital video, multispectral,
and thermal-imaging cameras on the aircraft. The cameras give scientists
the ability to "see" reflected and thermally emitted electromagnetic
waves not otherwise visible to the human eye, according to Thomson.
The plane can also be equipped with digital still cameras, which can have higher resolution than video cameras. A computer program uses a Global Positioning System (GPS) to determine when the plane passes over a desired area of the field and activates the camera's shutter. The slight lag time that occurs with digital camera shutters is accounted for in the program.
Once images have
been retrieved from
them to create
a mosaic for
mosaic was used
in a study of
ponds near Lake
Agricultural aircraft can be flown much lower than larger planes. "Flying low avoids interference experienced with satellite images, which requires atmospheric corrections," Thomson says. But low flights limit the ability to capture images of large areas all at once. That problem is overcome by "mosaicing," which involves making multiple flights over the site and assembling many images taken over different portions. The challenge is to define the altitude that will result in the best images in terms of size, resolution, and area covered.
Putting New Method to Good Uses
Thomson and colleagues in the ARS Southern Weed Science Research Unit,
also in Stoneville, were able to distinguish between different weed
species and cotton and soybean plants in field studies. This demonstrates
the feasibility of using planes or ground sprayers to apply as little
pesticide as needed. Using digital data, the researchers could spot
weeds among early cotton at an altitude of 65 meters (about 215 feet).
Thermal images of cotton fields may help identify practices that favor
higher soil temperatures. Warmer soil correlates with earlier emergence,
which can benefit crop vigor in early-season cotton.
Water stress is a familiar problem to growers in the Mississippi Delta.
It is more difficult to detect crop water status by remote sensing in
humid climates than in semiarid climates because of limited canopy cooling
by evaporation. At the same time they are being used to spray pesticides,
agricultural planes can be used to obtain canopy heat signatures to
assist in irrigation scheduling.
Another major problem for farmers and ranchers in parts of the Midsouth
are imported fire antsred, black, and a hybrid of the two. Their
painful stings can ultimately lead to death for some people and newborn
livestock. Thomson is helping Stoneville researchers learn more about
the ants' behavior so they can develop more effective biological control
methods. They know that fire ant mounds heat up in morning hours more
quickly than the surrounding soil does. So the researchers are using
thermal cameras to measure infrared emission (heat) and locate the mounds,
which appear as bright spots in images taken from above.
Aquaculture could also benefit from remote-sensing methods. Thomson
and Paul Zimba of the Catfish Genetics Research Unit in Stoneville are
studying a way to detect harmful algal species in catfish production
ponds before the problem gets out of hand. The researchers can now identify
specific types of algae by color, visible on digital video shot during
the low-altitude flights. Unwanted algae are distinguishable by their
chlorophyll and carotenoid compounds. With enough data, the scientists
can predict when certain types of algae are present.
Another project is to find out why double-crested cormorants tend to
pluck catfish fingerlings out of some ponds but not others. Thomson
and Andy Radomski of the Harry K. Dupree National Aquaculture Research
Center in Stuttgart, Arkansas, think pond color and condition may have
some effect.By Jim
Core, Agricultural Research Service Information Staff.
This research is part of Crop Production (#305) and Integrated Agricultural
Systems (#207), two ARS National Programs described on the World Wide
Web at www.nps.ars.usda.gov.
Steven J. Thomson is
in the USDA-ARS Application
and Production Technology Research Unit, P.O. Box 36, 141 Experiment
Station Rd., Stoneville, MS 38776; phone (662) 686-5240, fax (662) 686-5372.
"Agricultural Aircraft Offer a Different View of Remote Sensing" was published in the March 2005 issue of Agricultural Research magazine.