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Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Tour Canada from space Québec City, Québec
 The heart of Québec is Québec City, the provincial capital, one of the oldest European settlements in North America and host to a famous winter carnival. In this partial view of the city, the combination of panchromatic and multispectral SPOT images allows both a coloured representation, as well as high definition or detail. The fine resolution shows much detail in the historic part of the city, as well as allowing interpretation of some of the industrial features of this port on the St. Lawrence River. The multispectral, or coloured nature of the merged image permits interpretation of some of the residential and recreational portions of the city.
Question: What is the dark linear feature starting on the bottom left corner of the image and ending below the centre: river, cloud shadow, escarpment? What clues do you have to help you choose the correct answer? [ Answer ]
About this Image
| Location: |
Québec City, Québec |
| NTS map(s): |
21L/14 (1:50,000) |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
October 25, 1989 |
| Satellites/Sensors: |
SPOT Multi-Spectral and Panchromatic |
| Resolution: |
6.25 m pixels |
| Image Area: |
4.5 by 4.5km |
| Image Features: |
Citadel, ramparts, Plains of Abraham, buildings, streets, neighbourhoods, trees, parks, rivers, industrial buildings, storage tanks, highways, shadows |
| Related Tour Images: |
Montréal, Québec; Winnipeg, Manitoba; Downtown Vancouver, British Columbia; Calgary, Alberta; Ottawa, Ontario; Toronto, Ontario |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
image texture, tone, brightness, spatial resolution, data integration |
| 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 2.12 4.2 5.7
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| Image Credits: |
Received by the Canada Centre for Remote Sensing
Processed and provided courtesy of RADARSAT International Inc. |
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Additional
Information: | Two satellite images were combined for this presentation of Québec City. One of these was a SPOT PLA scene, offering just a single channel, panchromatic view, but at the very high spatial resolution of 10 metres. The other was a SPOT MLA scene at the lower spatial resolution of 20 metres, but with three spectral bands. (Note: Actually, the combined image shown here, has been resampled to a pixel size of 6.25 metres! For a different example of two satellite images combined into one, see the Ottawa Landsat/SPOT scene.) The panchromatic scene and the multispectral scene, when combined, illustrate the benefits of each type of image: high spatial and spectral detail. How is this 'combination' made? How can a new set of pixels be created with the 'colour' of a multispectral'image and the fine spatial resolution of another? The answer: simple arithmetic! |
| Question: |
What is the dark linear feature starting on the bottom left corner of the image and ending below the centre: river, cloud shadow, escarpment? What clues do you have to help you choose the correct answer? |
| Answer: |
It is not likely a river, since it doesn't have the sharp riverbank definition that a river would have, flowing through a city. For contrast, note the appearance of the Saint Charles River on the middle left portion of the image. Also, a river would be expected to join the nearby St. Lawrence River, and there is no evidence of this.The feature is too narrow to be a cloud shadow, and besides, there are no visible clouds in the vicinity. An escarpment is the likely cause of this feature, for several reasons: a) it is an appropriate shape; b) an escarpment would be expected to break the street pattern and the land use on its two sides, and this feature evidently does just that; c) in the days when citadels and forts were being built, the choice of preference was high ground and therefore a nearby escarpment makes a lot of sense. |
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