The Rural Voice, 1985-09, Page 18Agriculture brings satellite
data down to earth
Picture a western rancher in one of
Canada's prairie provinces riding his
horse over the pasture to find the best
grazing area for his cattle. Instead of
following only his own instincts, he
has in his hand a plasticized satellite
image to guide him to the best pasture
during this season.
Remote sensing, dubbed "the
space age answer to resource
management," is the obser-
vation of the earth and its resources
from a distance (usually from a
satellite). In little more than a decade,
Canada has become an international
leader in remote sensing, especially in
agriculture. The satellite -sourced data
and photographs can help ranchers in
western Canada choose the best
pasture land, help farmers and
marketers in Ontario estimate the size
and locations of certain crops, assist
agricultural processing companies in
finding the best location for a new
plant, and can be applied to many
other agricultural situations, says
Robert Ryerson, Canada's Remote
Sensing Centre's chief of user
assistance and marketing.
Space-age technology isn't new to
the agricultural community. As early
as 1976, the Ontario Bean Producers'
Marketing Board hired the Canada
Centre for remote sensing, a branch
of Energy, Mines, and Resources
Canada, to estimate bean production
in Ontario. The board also wanted to
know if others could estimate the
bean crop as well or better than they
could.
For this assignment, as is true with
most projects, ground information
was required to supplement satellite
data. (Satellite photos can distinguish
soybeans and lima beans from white
beans and red kidney beans, but in
the two pairs, the partners are almost
impossible to differentiate). To cover
the four major bean -growing areas,
the satellite took four pictures of
34,000 square km. Ryerson estimates
that today the cost of the satellite im-
ages required for such a project
would be $3,500. That price combin-
ed with the money required for
16 THE RURAL VOICE
by Phyllis Coulter
ground work, data creation, and
analysis would add up to between
$10,000 and $20,000 today. This
compares poorly with the cost of
mail -out questionnaires used to
estimate production. In addition,
province -wide esimates of crop
acreage wouldn't be any more ac-
curate from the satellite than from
the questionnaires. "In this particular
case, the added costs of satellite work
do not warrant the increased preci-
sion," says Ryerson, who is also an
agronomist. But remote sensing
technology has increased tremen-
dously in the nine years since the bean
producers' project was undertaken.
Studying satellite -sourced data was
also part of the decision-making pro-
cess of a large milling company wan-
ting to locate a processing facility in
the area with the greatest concentra-
tion of its input crops. Remote sens-
ing showed where the crops were
specifically concentrated, and pin-
pointed an area where the company
could meet their major requirement
and also be near rail service for
transportation.
Remote sensing has vast potential
in a multitude of resource manage-
ment situations across the county.
For example, when gas pipelines were
to be installed through farming areas
in New Brunswick, the community
wanted specialty cropping areas,
especially potato fields, to be avoid-
ed. Through remote sensing, fields
where potatoes were grown in recent
years were determined, and a gas
LANDSAT-5, launched in March of 1984,
carries a Thematic Mapper (TM) sensor.
The Thematic Mapper senses the elec-
tromagnetic radiation reelected by the
earth's surface in seven specific regions
or bands of the spectrum, each band hav-
ing its own usefulness:
Band 1: Used for water body penetration,
making it useful for coastal water
mapping. It is also useful for
differentiation of soil from vegetation, and
deciduous from coniferous flora.
Band 2: Used to measure visible green
reflectance peaks of vegetation for vigour
assessment.
Band 3: A chlorophyll absorption band
important for vegetation discrimination.
Band 4: Useful for determining biomass
content and for delineation of water
bodies.
Band 5: Indicates vegetation moisture
content and soil moisture. Also useful for
differentiation of snow from clouds.
Band 6: A thermal infra -red band o1 use in
vegetation stress analysis, soil moisture
discrimination, and thermal mapping.
Band 7: A band selected for its potential
for discriminating rock types.
LANDSAT-5 operates from an altitude
of 705 km, scanning the earth's surface
between the latitudes of 78°N and 78°S.
The satellite is in a sun -synchronous orbit,
which means it always crosses a
particular latitude at the same local time,
for instance 11:20 a.m. for the latitude of
Prince Albert, Saskatchewan.
— Canada Centre for Remote Sensing