3. METHODS CONSIDERED IN THE TANG PROJECT
3.1 Remote Sensing
A large area has to be investigated for the Tang project.
Detailed surveys have to be carried out in the immediate
areas ofthe mausoleums. Nevertheless, there is a certain
interest in the areas inbetween the different sites and the
neighbouring regions.
The mausoleums have been erected at sites that were
carefully selected based on geomantic considerations.
Geomancy (feng shui, Ax) applies certain rules for the
construction of tombs and buildings. Some are relatively
easytounderstand, suchasthe requirement of a mountain
towards the north which is believed to protect from evil
influences, or the presence of water in a certain direction,
others are of more esoteric nature and can supposedly
only be recognized by experienced geomancers. Since
research in this matteris part of the project, maps including
elevation information are needed. This has been achieved
by images, DEMs, and perspective views from SPOT
data. The potential of these products, although well known
in the remote sensing community, is not yet known
everywhere in archaeology.
Figure 2: Jingling mausoleum, 1: 50 000
Originally, unprocessed SPOT P scenes were used for
orientation in the field. Lateron, these scenes were geo-
referenced with the aid of GPS control points and
resampled to the specific Tang project map projection. In
the meantime, an improved version is available, adding
color from a simple classification based on SPOT XS data.
Also, vector overlays can be added, showing the basic
components of archaeological interest (mausoleum walls,
towers, stone sculptures and monuments, attendant
tombs), and topographic information (access roads,
contours). Since all this information is kept in different files
in the same data base, it can be combined as it is needed
for scientific investigations, publications, exhibitions, or
information for tourists when the sites are made acces-
sible to the public. As an example, figure 2 shows the
50
Jingling mausoleum area with all information of archae-
ological significance overlaid from the vector database
derived from tacheometric surveys.
With DEMs from SPOT images, improved and checked
by the local tacheometric surveys, all products mentioned
above can be overlaid with contour lines and/or shown in
any perspective desired. In addition, a short movie has
been produced, showing a virtual flight over the area.
Information about aspect and slope can be extracted and
used for research in geomancy. Since most mausoleums
are in areas where steep mountain slopes rise from the
loess planes of the Wei river, all presentations showing
three dimensions are quite impressive. Figure 3 shows
Qiaoling mausoleum as seen from the south.
In the case of the Tang project, only few details of
archaeological interest can be found in the images. As
mentioned above, the buildings have vanished. Since the
material used, loess, is the same as the surrounding soil,
no difference in appearance can be found. Even in the
field, investigations can only be made by lowering drill
holes, and judging the density of the loess material. One
important exception are the various mounds, however.
Most of the ancient towers of the mausoleum walls and
gates are still visible as mounds. As an average, they have
a more or less circular base of 10 - 20 metres in diameter
andthey rise about 5 mabovethe surrounding area. Some
additional tower sites are located far outside the mauso-
leums towards the south. In SPOT imagery the mounds
deriving from towers can only be detected in very few
Figure 3: Qiaoling mausoleum, perspective view
cases. This is not really a problem since these objects are
all found in the field surveys because of their predictable
location.
As far as the mounds of the attendant tombs are con-
cerned, the matter is somewhat different. More than one
hundred of those satellite tombs may belong to one
mausoleum. Also, tombs erected by earlier or later
dynasties may be encountered. Their locations have not
yet been documented with sufficient completeness and
accuracy. A systematic search using remote sensing tools
is useful. This is also promising since many tomb mounds
are larger than the tower mounds, with diameters in the
range of 20 to about 60 metres and corresponding ele-
vations.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
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