Geography Reference
In-Depth Information
Squared error) was about 588 m in F and P maps, ranging between 18 and 1,320 m in F map
and between 85 and 1,650 in P map; it was more constrained in L map (mean: 452 m; range:
29 รท 1,068 m). The residuals appear to be lower in the map centre, whereas they increase in
size in the peripheral areas. This is the classical border effect due to the polynomial
transformation associated to the lack of reference points in the area. But in this specific case
it can be supposed that the effect can be due also to other reasons, such as the survey
technique locally adopted, accidental or intentional drawing errors, etc.
Figure 3.
Overlay of the three ancient maps, georeferenced by means of a second order polynomial
transformation, on present high resolution satellite images (in
Bing Maps
TM
environment).
3.1.2. Study of map deformation
Comparing an ancient map with a present one allows evaluation and representation of the
deformation degree of the former. Map deformations can be induced by physical
alteration of the analogical support (a very frequent case for ancient maps) or by the old
type of cartographic transformation (that frequently is unknown to us, and usually quite
different from that used today and inducing less constrained deformations), or finally by
surveying and drafting errors. Map deformations can be very high for ancient
cartography; therefore, their assessment is essential in order to use the old samples for
further studies (Livieratos, 2006). The assessment of map deformations consists in
calculating some parameters from a comparison of the ancient map with a modern one as
a reference (usually a present cartography to an appropriate scale, i.e. comparable with
