Image Processing Reference
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Table 8.1 Average prior probabilities for housing density derived from census estimates, and
results from maximum likelihood classiications using equal and unequal prior probabilities based
on area estimates compared to census numbers
Average census prior probabilities
Low density
Settlement
Medium density
High density
Total/absolute
Bristol
0.094
0.297
0.627
1.0
Swindon
0.155
0.266
0.579
1.0
Bath
0.247
0.237
0.516
1.0
Taunton
0.104
0.302
0.594
1.0
Area estimation (%)
Bristol equal priors
+12.13
−5.04
−7.42
24.59
Bristol unequal priors
+7.44
−9.89
+2.13
19.46
Swindon equal priors
+11.58
−8.18
−3.94
23.70
Swindon unequal priors
+8.51
+5.56
+4.07
18.14
Bath equal priors
−2.79
+9.94
−8.20
20.93
Bath unequal priors
−1.09
+5.19
−4.11
10.39
Taunton equal priors
+2.35
+4.22
−5.26
11.83
Taunton unequal priors
−0.88
+0.68
+0.31
1.86
Fig. 8.1 Samples of local prior probabilities displayed alongside a Landsat TM 7 natural color
composite for the city of Bristol. Local prior probabilities are generated from housing data
recorded by UK Census of Population and are represented by census collection units called enu-
meration districts (e.g. 09DDFA01, 09DDGH21, and 09DDFZ29)
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