VERY LARGE SCALE MAPPING OF THE ARCHAEOLOGICAL SITE IN CERVETERI (ITALY): DATA
COLLECTION FROM DIGITAL AUTOMATIC D.T.M., ORTHOPROJECTION AND ANALYTICAL
STEREOPLOTTING
Raffaella BOLOGNA, Maurizio MINCHILLI
Dipartimento di Architettura ed Urbanistica
Politecnico di Bari
Via E. Orabona 4, 70125 Bari (ITALY)
email: minchilli@dau02.poliba.it
raf@dau02.poliba.it
Commission VI, Working Group 3
KEYWORDS: Aerial archaeology, photogrammetry, digital orthophoto.
ABSTRACT
The systematic field survey, during the archaeological excavations, is the fundamental methodology to
archive geometric and qualitative data for stratigraphic analysis. The data collection for cartographic
purposes are divided, for archaeological use, in three representational levels: territorial, whit scales from
1:25.000 to 1:5.000; urban, whit scales from 1:2.000 to 1:500 and archaeological details, whit scales from
1:100 to 1:10 and sometimes 1:1 for smaller objects.
We test the possibility to use digital large scale orthophotos, at urban scale, for data planimetric collection
and easy updating of site modifications. The first step has been the construction of detailed 1:2.000 digital
map of a large area next to the city of Cerveteri; then we try to construct a Digital Terrain Model, using image
matching tecniques, from the same medium scale photographs used in analytical stereoplotter. The obtained
geometric data base, with a grid 10x10m, was integrated with manual correlation for20%ca of the points.
Another aerial coverage, five months later, has shown a changed archaeological site situation with a larger
photo scale (1:2.300). Also these photos have been automatically correlated, with a grid step of 5x5m, and
orthoprojected. The construction of the new D.T.M. has been more difficult, because of the bad matching of
images taken from low altitude aerial coverage. For this reason the new nodes integration has been much
more expansive (about 50% of 3.027 points).
1. introduction
The study of archaeological sites of extension
larger than 10,000 mq requires the use of
systematic surveying methodologies of low
average price, with the contemporary requirement
of mapping with numerous details structural and
architectural elements having dense texture.
The photogrammetric coverage, for archaeological
purposes, must be executed with schemes that
greatly vary in relationship to oblique camera axes,
aerial platforms, use of captive balloons etc..
This paper reports on some experiences made
using normal aerial wide-angle photos of large and
very large scale. The aerial medium altitude flight
has been planned to the coverage of the whole
archaeological site, located to the east of the city
of Cerveteri near Rome. The aerial photographs,
taken from a relative height of 1,050 m, have got
an adequate photo-scale to plottings up to 1:
2.000. Subsequently, during the normal
prosecution of the archaeological excavations, it
has been possible to perform a new aerial
coverage at very low altitude, with images scale of
1: 2.300. This kind of photo-recording is very
critical in the respects of the forward motion, that
strongly requires the use of F.M.C. film magazine.
At this very close range from the archaeological
surface (ca 250 m) the visibility of the smaller
texture is potentially very high, and the obtainable
accuracy allow plotting up to 1: 200.
Later it will be illustrated the experiences
concerning the analytical plotting for large scale
and digital image processing for very-large scale
restitution.
2. Analytical stereoplotting
The requirements of the archaeologists, during the
of excavation progress, have been essentially
those of a systematic survey on the field for a
stratigraphy reconstruction of their works. This
repeatabilty of the photogrammetric
measurements, very similar to the one present in
the analyses of the loaded structures deflection, it
makes the topographic control points survey
limited only to the first cycle of measures. It results
in fact very rare that the area of excavation could
interfere with the location of the artificial targets or
with that of the photographic points.
