ANALYTICAL PHOTOGRAMMETRY FOR THE SURVEY OF THE GOLDEN ALTAR OF S. AMBROSE'S 
BASILICA IN MILAN 
Elena Baj, Associate Professor, University of Milan, Italy 
Commission V, Working Group 4 
KEY WORDS: Artwork, Close-range, Metric, Projector, Restitution, DTM 
ABSTRACT 
The golden altar of the Saint Ambrose's Basilica in Milan is considered one of the great wonders of the goldsmith art. It was 
decided that, before starting with necessary restoration work, it would be useful to make a photogrammetric survey of the altar, in 
order to determine its state at present and therefore to be able to monitor any deterioration with time. Since permission would not 
be granted to place targets on the altar, the single-photogram raster-photogrammetric method was used for the analytical restitution 
of more than 1000 points for each side of the altar. Actually a mesh of points with a reference system was projected onto the object 
by a metric projector and only one photogram was necessary for restitution of the projected points. To each point projected on the 
object correspond two plate coordinates on the photogram and two plate coordinates in the mesh. The plate coordinates were 
measured using a precision monocomparator. A specifically designed software was employed to calculate the 3D coordinates, XYZ, 
from the above mentioned plane coordinates. The photographs were taken with two cameras positioned symmetrically to the 
middle of the altar and a metric projector central to the altar. The two stereoscopic photograms allowed the restitution of the points 
which were inside the mesh of projected points. Several photograms were taken with different kinds of film, both coloured and 
black and white, and the best were chosen to identify the bas-reliefs. 
22 m long, 1.1 m tall and 1.3 m wide, has, in time, suffered 
some damage. The Abbot of Saint Ambrose decided, in 
The golden altar of Saint Ambrose's Basilica in Milan is a conjunction with the Superintendent for the Artistic and 
work of great artistic value and is considered one of the Historical Artefacts, that it would be useful to create a precise 
wonders of the medieval goldsmith art. It consists of a record of the present state of the altar by photogrammetric 
rectangular wooden case, panelled with leafs of pale gold or in survey, in order to monitor any deterioration with time. Fig. 1 
silver. The leafs mostly represent events in the lives of Jesus shows the East side of the altar. . 
Christ and of Saint Ambrose.The altar, which is approximately 
1. INTRODUCTION 
  
Figure 1 East Side of the Golden Altar of Saint Ambrose Cathedral in Milan 
22 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
This work w: 
AGIP S.p.A. 
highly special. 
The equipmen 
(a)Two large 
Jenoptik-Jena 
with a Ho 
photogrammet 
(b) A metric | 
direction of th 
UMK camera 
(c) A synch 
photography. 
3. 
The photogra: 
the objective