You have developed 6 Principal Components using 6 bands of a Landsat ETM+ image
ID: 293798 • Letter: Y
Question
You have developed 6 Principal Components using 6 bands of a Landsat ETM+ image (excluding band 6, which is the thermal band). The following table shows the correlation of each Principal Component with each Original Band.
ETM+
PC Band
Band
1
2
3
4
5
7
1
0.649
0.726
0.199
-0.014
0.049
-0.008
2
0.694
0.670
0.178
-0.034
0.004
0.157
3
0.785
0.592
0.118
-0.023
-0.018
-0.075
4
0.894
-0.342
0.287
0.017
-0.019
-0.000
5
0.989
-0.084
-0.112
-0.032
0.030
0.000
7
0.961
0.181
-0.152
0.065
-0.122
0.004
If you are planning to use 3 PC bands to create a composite that will enhance the vegetation (similar to a standard false color composite for ETM+ being 4-3-2), which 3 PC bands would you choose? Explain your choice clearly. (HINT: You should choose a PC band that has high correlation, for example, with bands 4, 3 or 2 individually but relatively low correlations with all other bands).
ETM+
PC Band
Band
1
2
3
4
5
7
1
0.649
0.726
0.199
-0.014
0.049
-0.008
2
0.694
0.670
0.178
-0.034
0.004
0.157
3
0.785
0.592
0.118
-0.023
-0.018
-0.075
4
0.894
-0.342
0.287
0.017
-0.019
-0.000
5
0.989
-0.084
-0.112
-0.032
0.030
0.000
7
0.961
0.181
-0.152
0.065
-0.122
0.004
Explanation / Answer
first band 1 because its value range between 0.649-0.989 so these band has a narrow range where it is correlated to itself but whereas it is not correlated to any other band so well.so it will provide a good quality of data without any overlapping of data. these will give us details about the original image.
second and third band we may choose is band 3 and 4 these has too very narrow range .so data will be highly correlated and will give absolute data.
using band 1 will have high percentage of correlation.
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