International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
Germany: complete, if 'permanently water leading,
else at a length > 500 m
Denmark: Length > 50 m, or if they are important for
the continuity of the hydrography network.
Finland: Width more than 2 m, exception in forest or
If they are important for the continuity of the
hydrography network.
Sweden: Length > 250 m
Global Schema: the attributes 'permanently water
leading" and 'important for the continuity of the
hydrography network' are not included into the
selection. Concerning the length and width of the
watercourse the least common denominator is defined.
So all watercourses with more than 250 m length or
more than 2 m width are recorded.
Attribute types and values of ERM and/or the FACC are only
included to the GiMoDig Global Schema if they are supported
by the majority of the countries, or if they appear to be of great
importance to the GiMoDig service.
S. VERIFICATION OF THE GLOBAL SCHEMA BY
MEANS OF TEST DATA
The process steps above yielded the preliminary Global
Schema, preliminary in the sense that it is result of a desktop
study but not yet tested on sample data from the NMAs.
For a robust definition, the preliminary Global Schema is tested
on sample data. Two test areas across the borders are defined
where the differences between national data could be examined.
One of the test areas is located in the Tornio/Haparanda area (1)
at the Swedish-Finnish border with a size of 10 x 10 km, and
the other at the Danish-German border from Hojer/Sylt to
Augustenborg/Kappeln with a size of about 100 x 30 km (2).
Figure 1 shows the location of the test areas.
Figure 1: Location of the test areas
The analysis of test data showed that some elements of the
Global Schema should be adapted to the situation, and that the
content of the national core topographic databases is not
sufficient in some cases and therefore data has to be acquired
from additional sources. In the following some of these issues
are discussed.
5.1 Missing feature types
As already mentioned in chapter 4.3 the initial goal of using the
least common denominator of national databases for the Global
Schema could not be realized because important feature types
would have been excluded. The actual Global Schema contains
some elements that have to be acquired from sources other than
the core topographic datasets.
In Germany the ATKIS specification considers buildings to be
derived from cadastre databases by means of automatic
generalisation, but these topographic objects will not be
available before finalisation of ATKIS in the year 2006. For
GiMoDig they have to be acquired from the cadastre databases.
The 'Contour Line' is an optional feature type in ATKIS, it is
provided by some but not all German Landesvermessungsámter.
For the GiMoDig application they are computed from the
Digital Terrain Model (DTM).
The Danish core topographic database does not include the
feature type 'Ocean'. It has to be created from 'Coastline' data
and/or 'Administrative Units'. 'Grassland' and 'Cropland' are
both not available in the TOPIODK but are added from the
Danish Ministry of the Environment.
Figure 2 shows the major deficits of the Danish and the German
databases in an example of the border area near the German city
Flensburg. It illustrates the lack of individual buildings and
contour lines in the German ATKIS dataset and the lack of
grassland and cropland in Danish TOPIODK dataset. Other
elements of land cover such as built-up area, forest and lake are
present in both datasets.
© KMS/BKG 0 500 1.000 1.500 2.000 2500 m
LLL N 1 Li}
Figure 2: Differences between Germany and Denmark
In the case of Sweden, only the major buildings are recorded.
So a complete record of buildings from the Swedish
municipalities is required for the GiMoDig prototype.
Furthermore, 'Grassland' and 'Forest' are so far not included in
the Swedish dataset. Finland lacks data for 'Built-up Area' and
polygon feature type 'Forest'.
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