CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
3. THE ACQUISITION MODES
The DM is the case when the old map can be safely scanned
with this mode. Depending on the size of the map, the sup
porting material and on the sensitivity of the drawing or print
ing, several types of high-resolution scanners can be used diffe
ring each time in:
■ Format.
■ Placement of the map and the type of the earner
motion; Mechanics of the moving sensor.
■ Resolution; Sensor properties.
■ Lighting type and intensity.
■ Cost.
■
In cases DM is not applicable, the photogrammetry-prone indi
rect mode (IM) has to be implemented. Here, proper digital and
/ or analogue photo cameras can be used, IM-dc and/or IM-ac
respectively, the latter requiring a further step, the a-posteriori
external scanning (IM-ac/d).
In each mode, dfs of the old map original are acquired using the
following hardware:
■ DM: Hard-copy scanners.
■ IM:
- IM-dc; digital cameras.
- IM-ac; analogue cameras, provide film sli
des and film diapositives which can be then
digitised using film scanners, IM-ac/d.
In this way, three main types of dfs of the same old map can be
generated by:
■ The DM,
■ the IM-dc and the
■ IM-ac/d.
Attention should be focused on the results obtained from the
use of different types of dfs-generating scanning devices in the
DM case, from the technical specifications of the digital and/or
analogue cameras in the IM case and from the use of different
types of dfs-generating scanning devices in the IM-ac/d sub
case.
4. THE INDIRECT MODE
The nature of the old map implies that in the most of the cases
it is proper to use the IM image capturing procedure. In this ca
se, both IM-dc and IM-ac lead to the very need of applying
photogrammetric methods and techniques. The IM-ac/d variant
introduces some additional issues related to the scanning pro
cess. Due to the state of the art in digital photography, the IM-
dc case needs rather high cost investment and it still requires
skills, which are not yet the common case in the every-day life
of professional photography. In this context IM-ac seems to be
the prosaic case and the indeed main stream in old map
documentation. The generation of the relevant dfs is an a-
posteriori process associated to the IM-ac/d.
It is needless to say that not only the IM procedures but also the
DM counterpart, introduce a variety of errors and image altera
tions that need to be first identified and then removed before
final expert analyses are performed on the “restored” map ima
ge. A typical example is the well-known image distortions due
to the inherent in any photo acquisition procedure central pro
jection. These distortions are present in any map image derived
by either IM-dc or IM-ac together with other errors, which
should be removed in order to obtain an ortho projection of the
map’s image, which can be easily done using off the shelf recti
fication software applications.-
V
Results
Figure 1. The proposed flowchart for old maps scanning and
unified photo/carto digital processing.
