Geography Reference
In-Depth Information
landmarks), or, finally, the involvement of more than one person in the surveying works. As
explicitly stated in some cartouches, the morphology of some depicted land areas can have
been taken from other previously developed cartographies; those areas are not explicitly
highlighted by the authors, but it is possible to infer their locations by excluding zones
where explicit signs refer to specific surveying techniques (i.e. sighting tracks, length
measurements, red reaches, bathymetric surveys). It can be hypothesized that some
topographical elements characterized by former drawings (e.g. in L map, see Paragraph 4.6)
were derived from previous cartographic documents. In fact, some visible former drawings
(e.g. Figure 10b) are placed in peripheral areas where residuals from the georeferencing
process are higher than those obtained in other areas of the map.
Other kinds of former drawings probably refer to corrections made by the authors over
time: they can denote real environmental changes in shape and/or location of the
topographic elements, or also intentionally-made corrections. The first ones can be
highlighted by a roughly deletion of previously drawn elements (see Figure 10a), whereas
the second ones seem to have been hidden by the authors by means of a brush stroke
covering. This is the case of an astonishing map “correction”, well recognizable in F map
(Figure 1a), probably done at an early drawing stage. For that detail it was thought that the
northern cluster of islands had been northward-shifted by the author for an unclear reason.
This could be supported by both the comparison with the other maps and the existence of a
wide area with no clear topographic detail lying immediately south of the delta coast.
Hence, a possible verisimilar original map appearance could be that shown in Figure 13: it is
a true “false case”, generated by means of a simple “surgical” operation performed in a
digital environment, in the opposite direction compared to the alleged author intervention.
It must be noticed that the southward-shifted cluster of islands coincides perfectly in its
morphology with the part of islands remained untouched.
The above described operation could now be attempted in all the other areas of F map with
already evidenced anomalies (Cremonini & Samonati, 2009), allowing a complete
regeneration of this ancient map. This could be an interesting way of approaching the study
of pre-geodetic maps.
5.1. Georeferencing of the “false case”
The presence of intentionally-made corrections could explain why some areas, differently
represented in F map in respect to P map (whereas in L map the represented land is
smaller), maintain an unclear post-georeferencing deformation in F map. In order to
demonstrate this assumption, a comparison of the new product (the “false case”) with
present cartography via modern georeferencing methods was made. In Figure 14 the
overlay of the “false case” on present high resolution satellite images (
Bing Maps
TM
environment) is reported; the map was georeferenced by means of a second order
polynomial transformation, as done for the original map (see Figure 3b). An analysis of
residuals of georeferencing could be the best way to check a real improvement in metric
quality of the new cartographic product in respect to the original one, but in this particular
