The creation of a transnational map
One aim of TEN was the production of a GIS-based map showing the
relevant structures for the implementation of a transnational ecological
network. In the following we want to describe the main steps of
the data preparation. An institue for computer science, OFFIS, had
the task of finding a way to handle the different data-formats and
to get the different map projections in one system, so that all
the participating regions could be visualized in one map.
Data preparation
Due to the variations in software used by the partners, the differences
between the co-ordinate systems of the countries involved, the various
methods of data-digitalization in the regions and certain other
factors it was, initially, extremely difficult to standardize and
collate the project data. The problem of getting different file
formats from the regions was not really relevant: It was possible
for the partners to deliver the data in most cases as an ArcView
shape file (*.shp) or in some cases as an ArcInfo format (*.e00).
This format was easily convertible in ArcView into a shape file.
It is possible to open shape-files with InterGIS (a software developed
by OFFIS). The output should also be in the shape-format, so that
the partners can work with the maps with ArcView. A bigger problem
was the fact that the data were delivered in several different projections.
There is no international standard, so every country uses its "national"
projection - and of course there are innumerable others. It is absolutely
essential to have the same projection in every layer - otherwise
the different layers cannot be shown at the same time.
Only an approximate mathematical conversion of one system to the
next can be achieved, as they are based on varying projections of
the globe. Due to the discrepancies between the systems, extensive
re-definition of the co-ordinates was necessary, for which new formulae
were calculated and special software had to be developed. The different
projections of the regions had to be converted into geographic co-ordinates
(decimal degrees). This was done with the software ArcInfo by ESRI.
In ArcView it is possible to visualize this co-ordinat system in
other projections.
Contents of the layers
The regions were asked to deliver data which could be relevant for
TEN - especially ecological data about wetlands, rivers, spreading
of target species (otter), nature conservation areas and of course
the main topographical data like roads, borders, towns. The data
from the different regions varied on a large scale. There were also
significant differences in the density of data. In some regions,
for example, the surveying was extremely detailed, while in others
the digitalization of greatly enlarged aerial and satellite pictures
meant that only a 25 metre grid could be digitalized. Moreover,
certain features were recorded, in some regions, in terms of an
area (e.g. natural corridors) whereas, in other regions, these corridors
were given as lines. First of all it was necessary to have a closer
look at the data: Which information was given, which data were missing?
In some cases it was not possible to get the topographical data
from the regions (for example because of copyright problems). These
topographical data were bought from commercial geographical data
vendors. It was necessary to analyse if the different categories
are comparable. An example: The category of "nature conversation
area" seems to be the same as the German term "Naturschutzgebiet".
The translation is the same, but the contents and the data can be
very different. In this case existing layers had to be modified.
Finally five standardized legend categories concerning the relevant
ecological structures for TEN could be formed: wetlands and corridors,
enhancement areas, otters present, nature conservation areas of
different categories, waters The data consist of layers at different
scales. Some of them are very detailed and you can zoom them, for
example, to a scale of 1:5000 - others are very rough and it is
not appropriate to look at them at that scale - for example the
"wetlands & corridors" or "enhancement areas"
categories.
