LABORATORY - ELECTROMAGNETIC RADIATION PRINCIPLES
Objective - To further understand electromagnetic radiation principles and remotely sensing measurements.
Part 1: EMR principles
(1) What is the solar exitance at UVA (315nm to 400nm) and at UVB (280nm-315nm)? What is the ratio between the exitance at UV (A and B) and total solar exitance? What is the extraterrestrial solar irradiance at the UVA? Take radius of Sun as 6.955 * 105 km and mean distance from sun to earth as 1.496 * 108 km. Show your work. If you write a program for these calculations, please provide your codes.
(2) Calculate the total Earth's irradiance received by the moon. The distance between Earth and the moon is 384,403 km; the temperature of the Earth (considered as a blackbody) is 300 K; and the radius of the Earth is 6.371 * 106 m.
Part 2: Top-of-Atmosphere Spectral Radiance
Level 2 WorldView-2 products are delivered as radiometrically corrected image pixels. Their values are a function of how much spectral radiance enters the telescope aperture and the instrument conversion of that radiation into a digital signal. Therefore, image pixel data are unique to WorldView-2 and should not be directly compared to imagery from other sensors in a radiometric/spectral sense. Instead, image pixels should be converted to top-of-atmosphere spectral radiance at a minimum.
Top-of-atmosphere spectral radiance is defined as the spectral radiance entering the telescope aperture at the sensor altitude, which for World View-2 is 770 km. The conversion from radiometrically corrected image pixels to spectral radiance uses the following general equation for each band of a WorldView-2 product:
Lλ Pixel, Band = KBandqPixel, Band/λΔBand
where LλPixel,Band are top-of-atmosphere spectral radiance image pixels [W-m-2-sr-1μm-1], KBand is the absolute radiometric calibration factor [W-m-2-sr-1-count-1] for a given band, qPixel,Band are radiometrically corrected image pixels [counts], and ΔλBand is the effective bandwidth [μm] for a given band.
(1) Calculate the extraterrestrial solar irradiance at each World View 2 multispectral bands. Use the acquisition date to find the distance from earth to sun (show your work and use references), and the bandwidth as following:
|
Spectral Band
|
Band Pass
|
|
Coastal
|
0.401- 0.453
|
|
Blue
|
0.448- 0.508
|
|
Green
|
0.511- 0.581
|
|
Yellow
|
0.589- 0.627
|
|
Red
|
0.629- 0.689
|
|
Red Edge
|
0.704- 0.744
|
|
NIR 1
|
0.772- 0.89
|
|
NIR 2
|
0.862- 0.954
|
(2) Convert the World View 2 image DNs to at sensor radiance using the equation provided above. More parameters can be found from the IMD file.
This example of .IMD file is for the coastal band showing the absolute radiometric calibration factor (absCalFactor) and the effective bandwidth (effectiveBandwidth):
BEGIN GROUP - BAND C
absCalFactor = 9.295654e-03;
effectiveBandwidth = 4.730000e-02;
END GROUP = BAND C
(3) Using the corrected image, choose at least fifty pixels for each of the cover types identified in the image (at least three), and get their DN values (for all bands). For each cover type, please plot its mean and standard deviation in DN vs. Band. High quality figures are expected. A proper title has to be given to each axis (including the unit). In your report, you need to provide a caption to any figure included.
(4) Discuss the spectra you generated in (3) in the following aspects:
a) Describe the characteristic for each cover type (pay attentions to high absorption feature, and trend).
b) Compare and comment the properties of cover types in the imagery.
c) Compare and comment the difference between this one and the one you generated in the previous lab.
Attachment:- Assignment Files.rar