Additional
Information: |
Essex County in Ontario is one of the premier agricultural
areas of Canada. The soils and climate are particularly
suited to agriculture. A wide variety of cash crops (i.e.
tomatoes, strawberries, lettuce, fruit, etc.) are grown, as
well as wheat, corn and soybeans. Much of the southeastern
portion of the county (only partly represented on the image)
supports greenhouses. At one time this extremely flat portion
of southern Ontario was covered by a glacial lake. The
fluvial-glacial sediments from this ancient lake make
extremely rich agricultural land. The native prairie type
grasses of Essex and the surrounding counties were cleared a
long time ago for agriculture. Pockets of these native
grasses can still be found and support many bird and
vegetation species not commonly found in other parts of the
country.
This SPOT multi-spectral'image has a ground resolution of
20m and covers a total area of about 20km x 20km south of the
city of Windsor, Ontario. The towns of Harrow and Kingsville
can be identified by its lack of colour and characteristic
grid patterns of street. Numerous homes and farms are located
along all of the roads in the region.
The three spectral bands available from this sensor were
displayed in blue, green and red to create this colour
composite image. Band 1 (0.50-0.59m) or the green portion of
visible light is displayed as blue: Band 2 (0.61-0.68m) or
the red portion of visible light is displayed as green and;
Band 3 (0.79-0.89m) or near infrared is displayed as red.
The colour combination shown, gives the healthy, dense
vegetation a very red colour. The major vegetation types
(including the crops, trees, bush and lawns) are in red,
while areas lacking vegetation (roads, buildings and bare
fields) are displayed in shades of white and light blue.
Water appears dark blue to black, depending on the sediment
content and water depth.
Agricultural agencies, farming groups and governments use
such satellite images to identify crops and monitor crop
growth in an effort to forecast yields that will assist in
setting crop prices. Information is also used to determine
assistance that may be needed if there is a crop failure and
to map crop destruction due to environmental disasters.
SPOT's frequent coverage (about every 4 or 5 days at this
latitude) can provide information about disease to allow for
remedial action, and also about irrigation practices.
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| Answer: |
The combination of green, red and
near-infrared sensitivites depicted as blue, green and red
respectively is a traditional and useful way of showing
vegetated areas where the vegetation type, health or density is
of interest. The inclusion of the near-infrared band is the
critical choice, since this part of the electromagnetic
spectrum is particularly responsive to vegetation. For
instance, vegetation under stress often shows much reduced
reflectance in the near-infrared even before it shows signs
that are visible to the naked eye. This technique is also used
extensively to unmask camouflaged targets, since objects
painted green will be quite distinct from living vegetation
when viewed in this type of imagery. |
This SPOT MLA image represents an intensive farming area
south of Windsor, Ontario in Essex County. Farming activities include: growing
wheat, soybeans, corn and a wide variety of cash crops (i.e.
tomatoes, strawberries, lettuce, fruit, etc.). The healthy,
vigorous crops and other vegetation are represented by strong red
colours. In contrast are the fields showing bare soil, displayed as
blue-white. This band and colour combination has been used
extensively, even in aerial photography, to depict vegetation
features, because of its ability to discriminate among vegetation
types, density and stress levels. The extremely flat topography,
typical of the region, develops very slow
moving, meandering rivers, while near the lakeshore other drainage network shapes develop. The city of Kingsville is fairly easy to
identify on the lakeshore at the right edge of the image. 
