The Rural Voice, 1985-09, Page 19This is an artist's conception o/ the
RADARSAT satellite, a sophisticated new
remote sensing satellite being developed
by the Canada Centre for Remote Sensing
Scheduled for launch in 1990, RADARSAT
will carry an advanced radar technology,
Synthetic Aperture Radar (SAR),
which can "see" day and night in
any
kind of weather and will have
hundreds of uses. SAR is
especially effective in
forecasting northern ice
conditions, and can also
be used for crop monitor-
ing,
oil spill detection and
resource exploration.
—Canada Centre for
Remote Sensing
pipeline route was chosen to avoid
those areas.
Similarly, in northern Ontario,
remote sensing has assisted in general
route selection for Ontario Hydro
corridors. This is followed by low
level surveying to more specifically
design the route, Ryerson explains.
Often aerial photography sup-
plements satellite data. The Canadian
Centre for Remote Sensing operates,
in co-operation with industry, a fleet
of three aircraft equipped with
sophisticated optical radar laser sen-
sors. Data from these sensors is pro-
duced in either electronic or
photographic form. The electronic
data is directed to Canada's receiving
station in Prince Albert, Saskat-
chewan where it is recorded on large
magnetic tapes, processed, and final-
ly archived at CCRS.
Aerial or low level photography
has a number of uses which comple-
ment satellite work. Ryerson, who
received his Ph.D. at the University
of Waterloo and also studied at
1
McMaster, recalls an experience with
airborne photography early in his
career. As a student he interviewed a
farmer (who had one too many drinks
that day) about the crops on his farm
in the Niagara region. The farmer's
tomatoes were "withering on the
vine" due to poor management.
Ryerson was surprised to see the same
farmer on television shortly after.
The farmer was blaming a nearby fac-
tory's pollution for the damage to his
crop. Aerial photography from a
number of years proved this man's
fields were always inferior to his
neighbours'. "The photos showed
this guy was a lousy farmer then, and
still was." Conversely, aerial
photography can also show when a
farmer does have a legitimate claim
about pollution damage.
Infra -red film from aerial
photography can also help farmers to
locate tile drainage problems, or
allow them to access the work of their
custom sprayer or seeder. "Remote
sensing is not all razzle dazzle. You
can't do much if you don't know
about the ground," Ryerson points
out. Farmers and people who know
the ground are often particularly
adept at interpreting satellite infor-
mation, he says.
The most obvious disadvantage of
satellite information is that satellites
have lower resolution (ability to see
detail) than aircraft because satellites
are travelling 900 km above the earth.
In addition, data may be required
more frequently than it is available
from the fixed cycle of a satellite.
Satellites pass the same spot every 16
days.
Each year in Canada, small areas
of land about 1.7 km wide by 5 km
long are chosen for intensive study.
Air photographs and interviews with
farmers about these segments of land
determine what is actually there; it is
then compared to what the satellite
observes. In this way, scientists can
measure the errors made in inter-
preting satellite information. Using
information from a very small area,
researchers can correct the interpreta-
tion of satellite information from a
much larger area.
A satellite can distinguish between
ground areas as small as 0.4 hectares,
but it is difficult to discern certain
crops at certain times in the growing
season. It is admittedly difficult to
distinguish wheat and barley from
canola soon after germination; the
problem is magnified with the
distance and speed of a satellite. Dur-
ing the flowering stage of canola,
however, the satellite can easily
record the crop because of its bright
yellow flowers. The time when the
satellite can most easily differentiate
one crop from another is known as
the biological window of that crop.
LANDSAT, a commonly used
satellite for agricultural services in
Canada, allows us to take advantage
of the biological window of
numerous crops to create crop area
estimates. The first LANDSAT
satellite was put into orbit by the Na-
tional Aeronautics and Space Ad-
ministration (NASA) of the United
SEPTEMBER 1985 17