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Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Tour Canada from space Melfort, Saskatchewan
 How would you go about gathering information about agricultural activity across Canada? Groups like the Canadian Wheat Board and Agriculture and Agri-Food Canada certainly don't drive to every field collecting data on crop acreage and yield. Instead, they use remote sensing data that provide coverage of very large areas in an efficient and timely fashion. But what if there is cloud cover, fog or rain - all of which are common in the summer months when crop information is collected? These conditions would impair data acquisition by optical sensors (like the LANDSAT "Thematic Mapper") at important stages of crop development. The answer: microwave remote sensing. More typically known as radar remote sensing, this technique is being studied intensively for its potential applications in agriculture because of its unparalleled advantages. These advantages make radar remote sensing perfect for collecting information about crop type, area, yield, conditions, and practices, especially over large areas. This synthetic aperture radar (SAR) image of the Melfort area can not only be used to show an overview picture of the city and the agricultural activity in the area, but also to determine different crop types, detect variations in crop health or growth stages within individual fields, and it can be used for crop inventory via image "classification".
Question: Why is radar remote sensing considered much more useful than optical for data acquisition during cloudy, foggy, or rainy weather? [ Answer ]
About this Image
| Location: |
Melfort, Saskatchewan |
| NTS map(s): |
73 A/15 (1:50,000) |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
July 31, 1983 |
| Satellites/Sensors: |
CCRS CV-580 Airborne SAR, C-VV |
| Resolution: |
Approximately 9 metres pixels |
| Image Area: |
Approximately 10 km by 6 km |
| Image Features: |
Crop types, within-field variation, city of Melfort, image classification |
| Related Tour Images: |
Altona, Manitoba; Niagara Falls, Ontario; Fredericton, New Brunswick; Essex County, Ontario |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
image classification, contextual classification, supervised classification, image texture, tone, brightness, contrast, speckle, speckle filter |
| 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:
3.5 3.6 3.8 5.2
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| Image Credits: |
Some information adapted from Chapter 7 ("SAR Applications in Agriculture") of "Radar Remote Sensing: A Training Manual", Dendron Resource Surveys Inc., as well as from the City of Melfort homepage at www.cityofmelfort.ca. |
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| Question: |
Why is radar remote sensing considered much more useful than optical for data acquisition during cloudy, foggy, or rainy weather? |
| Answer: |
An airborne synthetic aperture radar (SAR) like Canada's satellite RADARSAT, collects data using the much longer wavelengths of the microwave portion of the electromagnetic spectrum, as opposed to the shorter visible or infrared wavelengths often used in optical data acquisition. These longer wavelengths pass easily through clouds and other atmospheric disturbances, making it possible to acquire images at times when it is not possible to obtain useful optical'imagery. The optical wavelengths, however, are more similar in 'size' to the intervening water and particulate matter in the atmosphere and therefore interact more easily with them. Also unlike optical remote sensing, radar permits the acquisition of high resolution data independently of solar illumination conditions - which means that images can even be collected at night! |
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