The Institute - September 2018 - 6

Hagness says. They actually grow on
dry vines in beds that are layered with
sand, peat, and gravel-known as
"bogs." Typically farmers then flood the
bogs. But long before a bog is flooded,
farmers and growers, as well as cranberry researchers, want to know how
many berries are on those vines.
The team's current microwave
sensing system is composed of a metal
waveguide mounted on a PVC support
structure that positions it above the
canopy. The waveguide sensor transmits electromagnetic waves toward
the ground and receives the reflected
signal. The device can scan about a
square foot at a time.
"Before we set out to develop
a first-generation prototype of the
cranberry-sensing system, we asked
Ben for a bunch of cranberries to
study in the lab," Hagness says. "We
sliced them open to measure the
dielectric properties of the flesh of the
fruit and confirmed that there was a
significant dielectric contrast between
the high-water-content fruit and the
surrounding leaves and vines-about
a 3-to-1 ratio."
The more berries in the canopy, the
more water there is for the microwaves
to interact with. The system converts
the measured signals into an estimate
of the number of berries within the
sensor's 1-square-foot field of view.
The team is designing its
second-generation prototype to be
suspended from a boom and transported by truck to anywhere in the
field that a grower wants to observe.
Portability is important, Hagness
notes, because the farmers want to
estimate spatial variations in the
berry counts across different growing
areas to accurately determine the
yield of berries that year.

RADAR
TO THE
RESCUE
The technology is
automating the
process of counting
cranberries for
Ocean Spray farmers
B Y A M A N D A D AV I S

TH E IN STITUTE S EP TEM B ER 2018

GROW I N G P O S S I B I L I TI ES

To help Ocean Spray farmers count cranberries, researchers at the University
of Wisconsin in Madison developed a prototype for a microwave sensing system
that can scan a small part of a cranberry bog at a time. The system then estimates the number of berries-a task that now requires manual labor.

number of berries in the canopy
beneath the sensor."
She worked with IEEE Fellow John
Booske, a professor of electrical and
computer engineering, and IEEE Graduate Student Member Alex Haufler, a
Ph.D. candidate in electrical engineering, both at the University of Wisconsin,
to turn Tilberg's idea into a working

prototype [above]. They tested their
device last year at two cranberry farms
in central Wisconsin. Now they're working on a second-generation prototype,
which they plan to try out this year.
HOW IT WORKS

A popular misconception is that
cranberries are grown underwater,

The university's work stands to have a
significant impact on the cranberrygrowing industry in the state. The
United States is the world's top producer, with an annual yield of more
than 340,000 metric tons-and more
than half of U.S. cranberries are grown
in Wisconsin.
"To take our microwave-sensing
expertise and apply it to something so
relevant to Wisconsin has been really
meaningful," Hagness says.
She says the group isn't aware
of any prior work on cranberry crop
assessment done by radar. One farmer
in Florida has expressed interest in
using the group's technology to count
the fruit on citrus trees.
"Going forward we'll consider working with other growers," she says, "to
see if our technology can be adapted
for estimating yield for other crops." ◆
THEINSTITUTE.IEEE.ORG

ALEX HAUFLER/UNIVERSITY OF WISCONSIN

E E E F E L L O W Susan Hagness and
her research group at the University of Wisconsin in Madison have
applied their expertise in electromagnetics to a number of areas
including medical imaging and cancer
therapies. Now her team is working
on a device to help cranberry growers with the laborious task of counting
their fruit.
The current method of estimating cranberry crop yield is to harvest
the berries within 1 square foot
(929 square centimeters) of a bog
or marsh, count them by hand, and
extrapolate from there. Because there
might be hundreds of berries per
square foot, the process can be timeconsuming and labor-intensive. Also,
the process is imprecise.
"There can be numerous varieties of
cranberries growing on any given farm,
and not all varieties yield the same
amount of fruit," Hagness says.
Growers have been looking for
a technological solution to more
accurately and efficiently estimate
the size and quality of their crop, she
says. Two years ago, Ben Tilberg, an
Ocean Spray agricultural scientist in
Wisconsin, contacted the university with an idea. (Ocean Spray, a
cooperative of more than 700 farms,
is a leading producer of cranberry
products. It is headquartered in
Lakeville, Mass.)
"He was generally familiar with the
concept of microwave radar," Hagness
says, "and wanted to see if microwaves
could be used to remotely sense the

Table of Contents for the Digital Edition of The Institute - September 2018