Case Study
Tell Ahmar (Til Barsib)
Urban Zone
See also: - Summary page
- City Wall and Monumental Architecture
- Isolated Farmstead - City
Wall Resistance Data With Magnetic Overlay
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These images show a survey area within the urban zone
of the ancient city. This area is used as a trash dump by the modern
villagers. The many "sharp" (high- amplitude, short-wavelength)
bipolar anomalies which are present in this data set are caused
by modern metal debris. These are not of interest, and can obscure
relevant data.
Architecture in this zone is probably mud brick or
limestone, or a combination of the two. The buildings may have a
first floor composed of many small rooms, or multiple building episodes
may be superimposed. The walls appear as subtle magnetic lows in
the data. These lows are typically around 5nT below the mean, while
even very small ferrous metal objects can cause both positive and
negative anomalies raging into the hundreds of nanoteslas.
Although the data in the shade plot image (top) has
been clipped to display a reasonable range of data, any subtle features
are obscured by the noise introduced by modern metal debris.
The shaded relief image (bottom) was created to better
display subtle architectural features. The data was processed by
replacing all data outside of the -2nT to -8nT range (which is typical
of presumed mud brick or limestone architecture in this data set)
with zeros. A median filter, which replaces each data point with
the local median, was used to "smooth" the data, making
a more coherent image when obliquely lit in false relief. It should
be noted that this shaded relief plot of the data is mainly for
display, rather than analysis. Relevant data which falls outside
of the range being displayed is lost. For example, the linear feature
that runs north-south from N20/E25 to N50/E25, and some large bipolar
anomalies along the west edge of the survey area are thought to
be ancient in origin, but do not appear in the shaded relief plot.
