Geography Reference
In-Depth Information
The other reason of the distortions in the early maps was obviously the imperfection of the
measuring instruments used then. In 16
th
century there were used so-called logs for
measuring the distances. Jenkinson used it for instance during his journey by Volga river,
whereas for measuring the latitude he used so-called astrolabe, the most popular device in
16
th
century which enabled him to measure the position of the sun or stars. This instrument
was still modernized and used until the 18
th
century. As far as the designation of the
longitude is concerned, it was still a very difficult task at that time. Therefore Jenkinson in
his map marked only latitudes on the frames of the map. The map has no cartographical net.
It was the reason why the author used her own method in the form of a rectangular net to
show the differences between the examined maps and in the same way to try to determine
its projection. Simply because well-known distortion net is possible to be used only if the
cartographical net is used. The method the author first time has shown in 1994 during the
implementation of the grant Project given by so-called Polish “State Committee for Scientific
Research” (in Polish KBN). Then, the author invented the method and shown in graphic
form in two poster sessions on Zurich (1994) and Vienna Conference (Szykuła, K., 1995).
Next in a sketch description in the publication from the national Conference in Pobierowo
(Szykula, K., 2008). However, its final graphic result the author is going to present in her
“Monograph”
- then to be evidently proven by specialists of geodesy. Now short
description should be presented to the readers to let them see what is a basic principle of
this method.
The nets of triangles have been depicted on every one of the maps, including contemporary
maps, which have been chosen to be compared with Jenkinson's and other 16
th
century
maps of different authors. The number of triangles could be assumed by the author himself.
In case of Jenkinson's map it has been used ten triangles. The points of cities, mouth of
rivers and so on have been used as a vertexes of the triangles. The triangle nets to be
compared were fixed in two position - first in natural position (according to the lower frame
of the map), i.e. the given orientation and the second one according to one of the side of the
triangle which has been chosen by the author, but fixed vertically for every one of the maps
the same. In this way it was possible to observe how the whole given figure turned out and
how subsequent triangles changed its angles, surfaces and sides of the triangles. Sometimes
they changed not only their shape, but also vanished at all or they overlapped. Every figure
with precisely measured angles of the triangles had been then introduced to the computer in
a special Program. The results on the printed triangle nets were noticeable at the first glance.
It was especially interesting when we turned the figures according to the same vertically
fixed side of the given triangle. Then we could define closer an orientation of the map, as
well as to compare the triangle nets depicted on contemporary maps, too.
Summing up the benefits of the method we can shortly mention them as follows: 1/
possibility to identify the non-existing projection, 2/ to notice the differences in the
localization of the subsequent points as cities, mouth of rivers and so on, 3/ to define an
orientation of the map and 4/ to find most uncorrected places in maps of our interest
according to subsequent triangles.
