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Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Tour Canada from space Toronto, Ontario
 What is this stark image of Toronto? It is the view from Canada's first remote sensing satellite - RADARSAT. As the name hints, the on-board sensor is a radar (a 'synthetic aperture radar') which both illuminated the scene, and then captured the backscattered radar pulses in order to compose an image. It can do this day or night, through clouds, smoke and rainOne of thousands collected since the satellite was launched in November, 1995, this image is full of interesting features. Note, for instance, that the railroad yards in Agincourt (A) appear just as bright as the skyscrapers in the downtown core (B). The runways at Pearson airport appear just as dark as the golf course fairways (D) of Etobicoke. In East York (E), we can see streets that change from dark to bright and then back again! Follow the above links to learn more about such radar phenomena.
Question: Why does Yonge St. (Y) appear white and Highway 401 (401) black? [ Answer ]
About this Image
| Location: |
Toronto, Ontario |
| NTS map(s): |
30 M |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
May 12, 1996 |
| Satellites/Sensors: |
RADARSAT Synthetic Aperture Radar, mode F4 |
| Resolution: |
39 m pixels |
| Image Area: |
30.5 km by 24.9 km |
| Image Features: |
Urban landscape, highways, central business district, airports, central business district, urban, residential, city, corner reflection, street pattern, river bank, apartment building, railroad, airport, golf course, fairway |
| Related Tour Images: |
Montréal, Québec; Winnipeg, Manitoba; Downtown Vancouver, British Columbia; Calgary, Alberta; Ottawa, Ontario; Québec City, Québec |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
RADARSAT, backscatter, diffuse reflection, specular reflection, corner reflector, SAR |
| 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 3.9 5.7
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| Image Credits: |
Received by the Canada Centre for Remote Sensing
Processed by RADARSAT International Inc.
Source image © Canadian Space Agency, 1996 |
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Additional
Information: | RADARSAT uses a 'sun-synchronous' orbit so that each image of any one area is recorded at the same local (solar) time. This is true for both ascending and descending orbits. Moreover, RADARSAT's 'dawn-dusk' orbit places the satellite's solar arrays in almost continuous sunlight. This allows maximum exploitation of solar power for recharging the batteries and therefore for image acquisition. Also, RADARSAT downlinks data to ground stations at a time when other remote sensing satellites do not, thus reducing conflicts in image reception scheduling. The orbit altitude is 798 km above the Earth's orbit, is inclined 98.6°, and its 'period' is 100.7 minutes. The RADARSAT SAR can capture data for up to 28 minutes and image up to 1.1 million square kilometres of the Earth's surface with each orbit. Data are downlinked in real time or stored on one of the two tape recorders until the spacecraft is within range of a receiving station. In Canada and the United States, these are located in Prince Albert, Saskatchewan; Gatineau, Quebec; and Fairbanks, Alaska. |
| Question: |
Why does Yonge St. (Y) appear white and Highway 401 (401) black? |
| Answer: |
Can you find these two key routes through the middle of Toronto? Yonge Street, a very straight line, starts in the very bright cluster of buildings in the downtown core and exits at the top centre of this image. Highway 401 curves through the scene from the bottom left corner, diagonally through the image to the top right. Yonge Street is framed on both sides by many tall buildings close to the street itself. It is actually the backscatter from these buildings that make up the many white spots that appear along this route. The street (pavement) itself, is quite dark in the radar images and can be seen in places where the surrounding buildings are not too dense or too tall. Sometimes the tall buildings on the side of the road produce a radar 'shadow' that falls on the roadway, contributing to the dark appearance The pavement of highway 401 is dark for a similar reason. The smooth pavement causes the incoming radar beam to bounce away from the radar instead of back to it, leaving a dark appearance on the image. Because there are no buildings very close to the pavement of 401, there is no shadow effect, nor the strong backscatter that would appear as a bright spots on the radar image. |
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