In remote sensing, one must understand the reflectance nature of an object if it

Question

In remote sensing, one must understand the reflectance nature of an object if it is going to be identified on an image. In situ and other reference data is often collected at the time of image acquisition. One form of reference data is the ground-based measurement of the reflectance of surface features to determine their spectral response patterns This might be done in the laboratory on in the field (in situ) using a spectroradiometer. This device measures, as a function of wavelength, the energy reflected from an object within its view. It is used primarily to prepare spectral reflectance curves for various objects. In this lab assignment, we will use data from a multiband radiometer that measures radiation in a range of spectral hands. You will compute radiometric data from previously obtained instrumentation readings and then plot the spectral reflectance curves on a graph. This will allow you to determine which bands are most useful fee target discrimination based on experimental radiometric data. Examine these curves and predict the contrast relationship between various targets By analysis of experimental results such as these, the scientist may be able to choose the proper spectral hand combinations for a given remote sensing goal. The objectives of this tab are to: Determine the most useful bards for target discrimination Identify features hated on spectral reflectance curves Plot your data on a single graph. Wavelength is plotted on die x-axis and reflectance is plotted on the y-axis. Remember to put units on your axes and to give your graph a title that tells the purpose of the graph. Determine which of bands available to you is best for discriminating between die following target classes: Vegetation and Soil Water and Soil If you were to choose only two spectral bonds to discriminate between all targets. which bands would you select and why? Why do our eyes perceive healthy vegetation ns green m color What is the standard spectral reflectance curve for almost all healthy green vegetation? How do you think the presence of moisture in soil will affect its reflectance? What are some of the factors that affect the reflective nature of water? Why is it important to investigate the nature of spectral reflectance curves from targets prior to planning a remote sensing data collection mission?

Explanation / Answer

2.

Best useful bands for discriminating vegetation and soil target, soil and water targets.

a. Blue band - [4500-5100 Angstrom (Å)]

Distinguishing soil from vegetation.

b. Short-wave Infrared (SWIR) band 1 - [1570-1650 Angstrom (Å)]

Discriminates moisture content of soil and vegetation; penetrates thin clouds

c. Short-wave Infrared (SWIR) band 2 - [2110 - 2290 Angstrom (Å)]

Thin cloud penetration and distinguish soil and vegetation

d. Near Infra-Red band - [7000 - 8000 Angstrom (Å)]

For soil and water discrimination

e. Near Infra Red band - [8000 - 1100 Angstrom (Å)]

For soil and water targets

3.

I will choose Near Infra Red band, since it can even penetrate through clous and moisture content soil and water and can give better reflectance image of the target compared to the other bands.

5.

Relative refractive index between water and soil is less than that of air and soil. This enhances the interaction of light with moisture content soil (absorption probability of the moisture content soil increases). In internal reflectance model, this will decrease the reflectance probability. Thus moisture content in the soil will affect its reflectance property.

6.

Factors affect the reflective nature of water:

a. Depth of the water.

b. Materials (chemicals, living things, soil, sediments, rocks, stones, etc) which are available in the water. Depending upon the materials (or objects) inside the water.

c. Surface roughness of the water

7.

Reflected radiation and spectral response paterns for different features (such as vegetation, soil and water) studies are very important and interesting. One should systematically study the different surface in different wavelength regions and should find the appropriate band or wavelength for a particular surface. It is an important tool for air photo interpretation. Basic principle (for choosing the suitable band for a particular surface) is, find the highest reflectance contrast between two objects (by comparing all available bands), which will distinguish the two objects (or two surfaces) most clearly.

So it is very important for interpretation and comparison studies.

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