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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 ]
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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):
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". |
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| 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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