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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
3- MATERIALS AND METHODS
Every point distribution is the result of a certain spatial process
at a given time and a given space. The distribution of points
(archaeological sites) on the landscape may have various
patterns. They may take the form of clusters or they may be
dispersed in a consistent distribution or their distribution may be
entirely random without any specific pattern. With spatial
archaeology there are various methods for understanding the
distribution of archaeological sites in landscape and thus it is
possible to detect spatial pattern from the point distributions and
changes in point patterns at different times. Quadrat Analysis,
which is one of the most common methods used in archeology,
was employed in this study. Quadrat Analysis is used when sites
are measured in terms of point rather than their weights. This
method evaluates and measures the changes of distributions of
points (the sites of the study) in terms of density and the number
of points in each quadrat. The density, which is measured in the
quadrat analysis, is compared to a hypothetical random pattern
in order to find out from which pattern it is derived. This
comparison is carried out within a framework of a spatial
statistic system and its outcome is to arrive at a pattern that
shows how the sites under investigation have formed. At the
beginning of the analysis, it is crucial to determine the number
and forms of the quadrat analysis. For this reason, in 2005 and
2006 survey seasons, we first overlay the study area with a
regular square grid (10m. x 10m.), and count the number of
points falling in each square. Using precision military global
positioning system (GPS) receivers with real time 5 m accuracy,
aerial photography, a sighting compass and landmarks on the
horizon, we were able to survey entire grids and mark the whole
desired archaeological sites. Another important point about the
approach to analysis of this research was determining the
number and size of the quadrats. The studies of (Grifith and
Amrheim 1991: 131) indicate that the required size of the
quadrats can be obtained by the following equation:
Size of the quadrat= 2A/r (1)
Where A represents the size of the area under investigation and
r represents the points in the distribution.
By adopting the above equation, it became clear that given the
right size, a quadrat has a width of 2A/ r when the quadrats in
question are selected in the form of a square. Therefore, given
the above correlation, it is possible to perform this calculation
when the quadrats are selected with the required size. The
number of quadrats can be obtained through the correlation n =
r /2. When the area under investigation was located within
coverage of quadrats, some of the quadrats were lacking in any
kind of archaeological sites whereas some quadrats which had
one, two, three, or more sites were distributed within. Then, the
frequency of the points within each quadrat was counted and
their density was measured (table 1).
impact on identifying the properties of the site. For instance, if
we envisage that the observed distribution pattern tends toward
clusters, then we will need to look into the factors of this
phenomenon. But if we encounter this phenomenon where the
sites are distributed without any specific pattern, this might
show that the usual factors such as environment which affects
the sites do not have any role here. In fact, other factors more
than the above come into play in site distribution and dispersion
(see the rest of the article)
Number of sites in
each quadrat
Observed frequency
0
38
1
8
2
4
3
8
4
1
5
2
6
2
7
3
32
1
Total
67
Table 1. Frequency distribution of 118 sites observedfrom the
eastern shores of of Urmia Lake
In order to see the difference between an observed pattern and a
pattern whose basis is a random process, we can use a common
method, namely Poisson Process (equation 2) which is a
suitable backdrop against which random point pattern can take
place in the form of numerical data or frequency data.
-A x
e A
(2)
Where e is the natural logarithm and x t is the factorial of x .
To illustrate the difference between the observed amounts and
the amounts obtained from Poisson process, a statistical and
analysis system and K-S (Kolmogrov Smirnov) were employed.
K-S is a statistical method which measures the differences and
similarities in statistics in frequency distribution. In running
K-S measurement, our (H ) hypothesis was that there is no
significant difference between the two distributions or if a very
slight difference is observed, this difference is seen either as an
error of sampling or a chance happening (Table 2).
4- RESULTS
In table 1 the distribution of sites within the quadrats can be
seen in such a way that 38 quadrats don’t show to have any kind
of archaeological sites and 8 quadrats exhibit only one site
within it. On the other hand, one quadrat contains 32 sites. A
glimpse at the frequency distribution of the sites within the
quadrats may reinforce the idea that the sites within the quadrats
tend to form in clusters. Even though this conclusion-up to a
point- can be borne out by site distribution analysis, real
corroboration occurs when the degree of difference and
similarity of the observed frequencies is gauged in a
measurement system in the form of statistics with a theoretical
distribution basis. The type of site dispersion pattern has a huge
The study of distribution pattern of 118 archaeological sites in
the eastern shores of Urmia Lake and which was conducted by
the use of archaeological ground survey in 2006 indicated a
clustered pattern for archaeological sites. It isn’t the aim of the
present article to identify the correlation of distribution pattern
and existing factors in the area, because understanding the
correlation of site dispersion pattern and environmental and
cultural factors in the region plus the correlation of their
interaction necessitates collecting and analyzing more pertinent
data which they are at the preparatory stage. Nevertheless, the
analysis which has been run so far reveals that up to a certain
measure site distribution pattern follows a clustering pattern.