| Port Renfrew, British Columbia |
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Tour Canada from space Port Renfrew, British Columbia
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 Three bands of Landsat TM imagery, one from 1991 and two from 1984 have been combined to show the changes in the temperate rain forest on the southwest coast of Vancouver Island area near Port Renfrew, British Columbia. This combination of data clearly indicates changes which have occurred in the forest during this 7 year period.
Mature forest untouched in either year, is dark green. Areas that were recently logged in 1984 appear in pink, while areas logged between 1984 and 1991 are portrayed in bright blue. Second growth or regrowth (regardless of the year) is indicated by lighter green shades. Logging roads can be identified by their shape (long, winding, linear features) appearing in shades similar to the forest region surrounding them.
Question: Why are there large areas of uncut forest which appear darker than adjacent areas of similarly uncut forest (top right of image)? [ Answer ]
About this Image
| Location: |
Port Renfrew, British Columbia |
| NTS map(s): |
92 C/9, 92C/10 (1:50,000) |
 Location Map: |
See a detailed map (1:1M) of the region |
| Image Date: |
July 17, 1984 and June 19, 1991 |
| Satellites/Sensors: |
Landsat Thematic Mapper (TM), Band 5 (1991), 4 (1984), 5 (1984) as R,G,B |
| Resolution: |
30 m pixels |
| Image Area: |
15km by 15km (each side) |
| Image Features: |
Forest change detection, logging roads, mature forest, forest clear cuts |
| Related Tour Images: |
Whitecourt, Alberta; Lac Nemiscau, Quebec |
| Related Glossary Terms: |
These terms from the CCRS Glossary may help you to understand this image and its interpretation:
additive colour, change detection, colour composite, image enhancement |
| 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:
2.6 2.8 2.12 5.3.1
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| Image Credits: |
Received by the Canada Centre for Remote Sensing
Processed and provide courtesy of RADARSAT International Inc. |
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Additional
Information: | The Landsat TM data used in the colour composite seen here, has a ground resolution of 30 metres and covers an area of about 30km x 30km over temperate rain forest on the southwest coast of Vancouver Island. Three bands of imagery, one from 1991 and two from 1984 have been displayed as red, green and blue to create this colour composite image. This combination of data clearly indicates changes which have occurred in the forest over seven years.
Red: 1991 TM Band 5 (1.55-1.75mm or Short Wave Infrared)
Green: 1984 TM Band 4 (0.76-0.90mm or Near Infrared)
Blue: 1984 TM Band 5 (1.55-1.75mm or Short Wave Infrared)
Landsat TM is used by forestry companies, Provincial and Federal Government Agencies and Environmental Organizations to monitor forest activities such as cutting, road building and reforestation. Satellite imagery is a valuable tool in assessing the environmental impact of forest activities. It can also assist in responsible forest management. |
| Question: |
Why are there large areas of uncut forest which appear darker than adjacent areas of similarly uncut forest (top right of image)? |
| Answer: |
Both the medium and the adjacent dark green areas represent
similar forest of similar condition. The differing tone represents
different illumination by the sun, since these areas are on
opposite-facing slopes. This phenomenon is one of the many challenges
facing visual interpretation of imagery. For automated (computer-based)
techniques, the use of digital elevation models (which can identify the
direction and degree of a slope) are used to eliminate this unwanted
effect. |
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