LABORATORY: ATMOSPHERIC CORRECTION
Objective - The molecular and aerosol constituents of the earth's atmosphere cause scattering and absorption of the incident solar radiation altering the spectral character of the irradiance reaching the surface as well as generating scattered light into the spaceborne or airborne sensor. Although the characteristics (brightness and spectral distribution) of the solar radiation outside the earth's atmosphere (known as the exo-atmospheric solar irradiance) has been measured repeatedly and is considered well-known, the characteristics of the radiation field received at the earth's surface is highly variable, dependent primarily on the solar angle and the optical properties of the atmosphere. The objective of this exercise is to help you further understand the components of at-sensor radiance and master the approaches to remove atmospheric effects.
Assignment: Atmospheric correction of remote sensing data using PCI Geomatica
In this exercise, you are required to go through the procedures of atmospheric correction on World View 2 data using the ATCOR model in PCI Geomatica software, and design an experiment to justify your results. Following are some important procedures you may need to perform:
(1) The pixel values in the World View 2 images from Lab 1 are "scaled radiance" which is also called digital number (DN). Therefore, in theory, a conversion from the scaled radiance back to the real at-sensor radiance should be performed first. Note that in Lab 2, we have already done that.
(2) Use ATCOR model in Geomatics algorithm library or FOCUS-> Analysis panel to perform the atmospheric correction. Before input the image into the model, you will need to normalize the pixel values into 0 to 100, and saved as an 8bit image.
(3) The description of input parameters of ATCOR is provided in the help file of the model. You can find out and calculate the solar zenith angle based on the sun elevation angle provided in the IMD file or based on the date and position information provided. The average elevation will set to a constant value of 200 km. Satellite angle can be also found from IMD file as well. Information regarding IMD file refer to vendor website.
(4) Compare the data before and after atmospheric correction for different types of ground objects. Plot them (radiance vs. wavelength, and reflectance vs. wavelength) for cover types such as: water, vegetation and road. Discuss your results, for example, you may find that the spectrum curve for vegetation after correction is different than that before correction.
Attachment:- Assignment File.rar