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NOTES ABOUT SATELLITE IMAGES ORTHORECTIFICATION 
OF ARCHAEOLOGICAL SITES 
C. Sena'* , C.A. Birocco? 
'Polytechnic of Turin, C.so Duca degli Abruzzi 24, Turin (Italy)- carmelo.sena@polito.it, 2ARTGeomatica, corso 
Bramante 91, Turin (Italy) - ca.birocco@jumpy.it 
  
Commission V, PS WG V4 
KEY WORDS: Cartography-Archaeology- Ortho-rectification-High resolution-Experience 
ABSTRACT: 
The comparison between aerial photographs and satellite images, with regard to their performance, is strongly actual: in fact, 
advantages and defects of both are well known. In. the past , low spatial resolution of satellite images was a limit in cartographical 
applications : now, the recent orbital platform are improving the data quality and, at the same time, make very large ground coverage 
possible. 
This feature, in digital orthorectification, is most interesting . it can reduce ( and, in some cases, eliminate) the need of image 
mosaicking, which is difficult or not possible using aerial photographs. 
Some experiences in our archaeological research unit ,have shown the capabilities of IKONOS images in Cartography on a large 
scale, related to land study on extended archaeological sites. The intent is to experience the differential rectification applied to a 
satellite image ( SPOT V, IKONOS, etc.) , comparing the obtained digital product with reference maps (as far as the scale 1: 2000). 
1. INTRODUCTION 
The aim of this paper is to investigate the potentialities for 
archaeological research teams to utilise high resolution satellite 
images (Ikonos, etc). 
Archaeologists have shown an interest in high resolution 
satellite images, from the initial first successful satellite launch 
in September *99, 
We would like to remind that the aerial photographs, and most 
recently the satellite images, represent one of the available tools 
for archacologist researchers who study the territory. 
The main aim of this study is the reconstruction of the 
settlements’ framework through an analysis of the land's 
organisation, the localisation of natural resources and the 
morphological characteristics. 
This study would also require the cartography at a medium- 
large scale (1:5.000/1:2.000): these scales define the level of 
planimetric accuracy of maps which this information has to 
guarantee. 
2. MAIN EXPERIENCES 
Our experiences in utilising the satellite images in archaeology 
have been mainly carried out in the *90s. 
SPOT images (P and XS) have been utilised for many years, 
before the last SPOT V generation, and they offered a geometric 
maximum resolution of 10 meters on the ground.(Fig.1). 
The control ground points (GCP) have been often defined 
through direct topographic measures (e.g. GPS) and, in the 
georeferencing polynomial models have been applied (since the 
affine transformation to the fourth grade). 
As mentioned before, the study of the land for archaeological 
objectives focuses on some aspects which we could define 
*macroscopics': the observed structures have relevant 
dimensions. 
The permanent divisions of the cultivated extensions, the shape 
of the roads and hydrological framework, the landscape and 
morphological peculiarities could be often recognised on the 
images characterised by a medium geometric resolution. 
The above mentioned context is, of course, quite relevant: for 
example we could obtain more interesting information from low 
resolution images in desert areas, rarely urbanised. in 
comparison to images with high resolution more suitable for 
urbanised areas where the human planning actions are more 
present. 
Three analyses could be at least carried out on the georeferential 
image: 
e Geometric analysis: it refers to some regular 
structures linked to the anthropic land organisation. 
On the basis of the geometric resolution it will be 
possible to identify only the biggest structures and 
therefore the main divisions (walls, cultivation, big 
communication paths, settlements etc ... ) or with 
highest resolutions it will be possible to also identify 
subjects with a minor dimension until to identify the 
perimeter of small constructions not visible but 
present underground. This analysis highlights the 
direction of anthropic signs recognised by the image 
as ‘traces’ with also the support of the bibliographic 
data, surveys and excavations.