| Essex County, Southern Ontario |
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Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Tour Canada from space Essex County, Southern Ontario
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 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.
Question: Why are many satellite images like this one, shown not in "natural" colours but in strange colouring where healthy vegetation comes out as bright red? [ Answer ]
About this Image
| Location: |
Essex County, Southern Ontario |
| NTS map(s): |
40J/2 (1:50,000) |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
August 3, 1988 |
| Satellites/Sensors: |
SPOT Multispectral mode (MLA) 3,2,1 (R,G,B) |
| Resolution: |
20 m pixels |
| Image Area: |
20km x 20km overview image (18km by 10km for more detailed image) |
| Image Features: |
Farming activities, drainage networks, meandering river, sewage lagoons, city of Kingsville, Ontario |
| Related Tour Images: |
Altona, Manitoba; Niagara Falls, Ontario; Fredericton, New Brunswick; Melfort, Saskatchewan |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
false colour, false colour composite, plant reflectance, red edge, vegetation index, leaf area index, normalized difference vegetation index |
| Related Tutorial Sections: |
These sections of the "Fundamentals of Remote Sensing" tutorial by CCRS will help you to better understand this image and its interpretation:
2.3 2.8 5.2 5.5
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| Image Credits: |
Received by the Canada Centre for Remote Sensing
Processed by and provided courtesy of RADARSAT International Inc. |
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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. |
| Question: |
Why are many satellite images like this one, shown not in "natural" colours but in strange colouring where healthy vegetation comes out as bright red? |
| 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. |
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