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Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Tour Canada from space Lac Nemiscau, Quebec
 Identifying the various types of vegetation shown in this Landsat TM image is quite a challenge. For the professional forester, who is familiar with both the forest environment and remotely sensed imagery, the task is not difficult. The forester can look at this image and classify similar land cover types into categories, which are identified by a letter code. This colour combination of the TM bands produces bright green areas indicating recent burns and regenerating forest, while the purple grey areas depict coniferous forest. Orange coloured areas are primarily deciduous forest and the small pink patches are typically wetlands and bogs. Lac Nemiscau and other small water bodies appear in black. A section of the Riviere de Rupert is visible in the lower portion of the image. A power transmission corridor is very evident in the image due to its artificially straight path which slices across the landscape.
Question: How can we tell that the straight, segmented line is a power transmission line rather than a road or a railroad? [ Answer ]
About this Image
| Location: |
Lac Nemiscau, Quebec |
| NTS map(s): |
32 N/7 |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
August 20, 1991 |
| Satellites/Sensors: |
Landsat Thematic Mapper (TM) Bands 4, 5, 3 (R,G,B) |
| Resolution: |
30 m pixels |
| Image Area: |
15km by 15km |
| Image Features: |
Forest fire burn, coniferous and deciduous forest, wetlands, treed heaths, Canadian shield, power transmission line |
| Related Tour Images: |
Central Northwest Territories |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
image enhancement, image texture, tone, brightness, contrast, contrast enhancement, contrast stretch, dynamic range |
| 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:
2.4 2.8 2.12 5.3
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| Image Credits: |
Received by the Canada Centre for Remote Sensing;
Processed by and provided courtesy of RADARSAT International Inc.;
Image interpretation courtesy of Dr. Jean Beaubien and Guy Simard, Laurentian Forestry Centre, Canadian Forest Service. |
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Additional
Information: | This image was acquired over an area of
northern Québec, and shows geology which is typical of the Canadian
Shield. If you look closely at the image, you can see a distinct trend
in the direction of the topography and surface geology. The surficial
materials and rocks in this region would have been strongly influenced
by the glaciers that once covered the area. Visual interpretation of the
image identified the following land cover classes (indicated by letter
code on the image):
- C - predominantly confierous
- D - predominantly deciduous
- M - mixed woods
- H - treed heaths
- R - old burn with veg. regrowth
- B - recent burn
- W - wetlands, bogs
There are no
other signs of human activity in the area except for the power transmission line
which can be seen running through the image on the right hand side.
Even place names
are sparse in this region. Beginning on the west side and extending
across the middle of the image, are about 5 large bodies of water joined
together. This series of lakes is collectively known as "Lac Nemiscau". |
| Question: |
How can we tell that the straight, segmented line is a power transmission line rather than a road or a railroad? |
| Answer: |
There are two places within this image where the straight corridor in question "jumps" over a narrow river. There is no evidence of a bridge, which would be required for a road or railroad. Power lines don't require a bridge - they are usually suspended across water bodies from towers. A detailed view of one of the power lines can be seen crossing Lac Nemiscau. |
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