Lab 3 Assignment – Radiometric & Geometric Corrections
[50 marks total]
Part 1: Radiometric
Explain the difference between Raw Landsat 8 DN values and TOA Spectral Radiance values. 60 words MAX [4 marks]
In the lab tutorial, you learned how to manually convert Raw Landsat 8 values into TOA Spectral Radiance. The Raw Landsat DN values for this question came from the SAME image you used in lab.
Manually calculate the new TOA Spectral Radiance values from the Raw Landsat DN values for Bands 1 through 4 shown below the coefficients will be the same ones you looked at in the lab tutorial.
Show your work. [8 marks]
Find an area of vegetation on your image and select a single vegetation pixel. Use the Inspector tool to generate the bar chart/numeric values showing the signal at each band. You will only consider bands 1-5 for this question.
300 words MAX [18 marks total]
Take screenshots of the chart AND numeric values for both Raw Landsat, and for Surface Reflectance (you do not need the TOA Radiance values for this question).
Discuss the differences between the two spectral profiles (pre and post correction) Bands 1-5 only: what part(s) of the EM spectrum are affected and why? (talk about all 5 bands individually considering scattering and/or absorption)
– What atmospheric attenuation processes are occurring, and are corrected for in the Surface Reflectance image? How do you know?
– Remember that absorption and scattering are wavelength dependent and will be different depending on band)
Refer to specific numbers in your spectral profiles to support your answer Hint: Raw Landsat and Surface Reflectance are presented in 2 different scales use the method demonstrated in the tutorial to put them into the SAME scale so you can compare the numbers. Do this for Bands 1-5 only.
(readings and lecture notes will help with this one)
PART 2: Geometric
If you wanted to map a mountainous region, limiting geometric distortions as much as possible, would you choose a satellite-based or aircraft-based scanning system? Explain why in terms of imaging geometry (readings). 100 words MAX [5 marks]
For this question, draw on what you learned through the slide presentation, and the 3-part video demo posted to Brightspace:
Consider this hypothetical scenario. You are an agricultural scientist studying crop diseases requiring the study of very specific biophysical parameters detectable using the image spectra.
You have imagery acquired from a hyperspectral airborne sensor (say AISA). It was quite windy when the imagery was acquired, so there is significant spatial distortion present in the raw data.
Provide a detailed description of ALL steps of the geometric correction process you would perform to make this image ready for analysis. Explain the reasons for your choices. 200 words MAX [15 marks]
