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| This [[attachment:ASAR_seaice_mixed_20080421_f32_1000x1000|ASAR image]] shows different sea ice types. Investigate the statistic of normalized backscatter value. What is the mean for the two prevalent sea ice types? Try to fit the image PDF with a superposition of two gamma distributions (ADVANCED EXERCISE). | This [[attachment:ASAR_seaice_mixed_20080421_f32_1000x1000|ASAR image]] shows different sea ice types. Investigate the statistic of normalized backscatter value. * What is the mean for the two prevalent sea ice types? Select homogeneous regions to answer this question. * Try to fit the image PDF with a superposition of two gamma distributions (ADVANCED EXERCISE). |
Radar backscatter statistics
The received power (intensity) of a radar system is proportional to the (normalized) radar backscatter coefficient
latex error! exitcode was 2 (signal 0), transscript follows:
as a function of frequency, polarization and incidence angle. The backscatter coefficient describes how much of the transmitted energy is backscattered from the surface media.
A (calibrated) ASAR image img(y,x)=I is made of the measured intensities I which can be directly related to the backscatter coefficient. A value of zero means that no energy is reflected from the surface whereas a value of one means the total reflection.
Exercise
This ASAR image shows different sea ice types. Investigate the statistic of normalized backscatter value.
- What is the mean for the two prevalent sea ice types? Select homogeneous regions to answer this question.
- Try to fit the image PDF with a superposition of two gamma distributions (ADVANCED EXERCISE).
from pylab import *
img=reshape(fromfile('ASAR_seaice_mixed_20080421_f32_1000x1000.dat',dtype=float32),(1000,1000))
close('all')
ql(img,vmin=0,vmax=0.3)
colorbar()
title('Sea ice radar backscatter intensity')