Environmental Engineering Reference
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inces, a clear negative autocorrelation with a light colour is seen in this part of the
figure.
14.4.3 Hot Spot Analysis (Getis-Ord Gi*)
Gi(d) and Gi*(d) statistics are described by Ord and Getis (1995) for the study of
local patterns in spatial data. Ord and Getis indicate the extent to which a location
is surrounded by a cluster of either high or low values. In other words, these statis-
tics show areas where higher-than-average or lower-than-average values tend to be
found near each other. Positive values indicate clustering of high attribute value
locations and negative values indicate clustering of low attribute value locations.
The more positive or negative the value, the more significant the results are. Equa-
tion 8 shows the usual form for Getis-Ord Gi* (Bailey and Gatrell 1995; Mitchell
2005; Scott and Warmerdam 2005). The analysis is carried out using Spatial Sta-
tistics Tool in ArcMap 9.3.
n
j
n
j
∑
∑
w
x
−
X
w
i
,
j
j
i
,
j
=
1
=
1
*
G
=
(14.8)
i
⎡
2
⎤
∑
n
j
⎛
∑
n
j
⎞
2
,
n
w
−
w
⎜
⎝
⎟
⎠
⎢
⎢
⎥
⎥
i
j
i
,
j
=
1
=
1
⎣
⎦
S
n
−
1
where
w
,
is the spatial weight between fea-
ture
i
and
j
,
n
is equal to the total number of features and:
x
is the attribute value for feature
j
,
j
∑
=
n
j
x
j
1
X
=
(14.9)
n
n
j
=
∑
=
2
x
j
−
(
2
1
S
X
(14.10)
n
As the most recent data should be enough to determine the most recent hot spot
locations of high electricity consumption, data for 2006 is used for this analysis
(
Figure 14.11
). The map shows that Istanbul, in the northwest corner of the coun-
try, was the most significant location of electricity consumption in 2006, with
more than 99% confidence. This indicates that there is a high chance that the area
can be considered a 'hot-spot'. Four provinces have the second biggest circles.
These are: Kocaeli, Bursa, Izmir and Ankara. These provinces create the second
significant hot-spot group with a confidence level of more than 95%. The common
features related to the electricity consumption of these provinces include a high
degree of industrial activity, especially high energy-intensive and high capacity
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