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Fundamentals of Remote Sensing

1.7 Whiz Quiz - Answer

1. Because both types of trees will appear as similar shades of green to the naked eye, imagery (or photography) using the visible portion of the spectrum may not be useful. Trying to distinguish the different types from aerial photographs based on tree crown shape or size might also be difficult, particularly when the tree types are intermixed. Looking at the reflectance curves for the two types, it is clear that they would be difficult to distinguish using any of the visible wavelengths. However, in the near-infrared, although both types reflect a significant portion of the incident radiation, they are clearly separable. Thus, a remote sensing system, such as black and white infrared film, which detects the infrared reflectance around 0.8 mm wavelength would be ideal for this purpose.
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2. By combining different channels of imagery representing different wavelengths, we may be able to identify combinations of reflectance between the different channels which highlight features that we would not otherwise be able to see, if we examine only one channel at a time. Additionally, these combinations may manifest themselves as subtle variations in colour (which our eyes are more sensitive to), rather than variations in gray tone, as would be seen when examining only one image at a time.
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