the
) in
for
the
1 of
nap
less
e in
lent
nies
lese
rea
rds,
vey
lies
, to
rere
The
'eas
ere
] to
ject
vel-
rdi-
988
ree
s in
new
ther
new
was
| for
ting
cale
ting
but
ons,
y, it
ised
4. PILOT PROJECTS
Parallel to the negotiations with the utility owners an in-house
plan to begin a fourth measurement of Denmark was established.
The plan was to create a digital basis for the production of the
base map 1:25.000. The cooperation with utility owners establish-
ing a digital map covering parts of Denmark forced this plan to be
abandoned. Instead a pilot project was created. The plan was to
use modern data acquisition techniques to develop and test a new
standard for digital mapping based on medium scale photogram-
metry.
In 1991 the Map and Chart Division was moved to a new address
in Copenhagen and a new Zeiss Phocus system was purchased.
The Phocus system consisted of one plotter P1, three modified and
digitized Wild A8 plotters and two working stations.
The aim was on one hand to create a digital map, which could be
useful to a broad range of users, from the inexperienced user to
the professional, and could form the future basis for map produc-
tion at the National Survey. It was a demand that the map data
could be used on a personal computer to serve the local munici-
palities in Denmark without restricting the advanced use of data.
The analog base map has more than 90 different codes (signatures,
areas with colours, patterns and so on) for objects shown on the
map. In the new standard for digital maps these were cut down to
less than thirty, but in a way that ensured that geometry still was
complete. As many object types as possible were defined as areas.
Roads, rivers and railways were defined as networks with
topology and nodes. The width of roads is linked to all centerline's
and there are defined nodes at all crossings. The buildup areas
were classified according to usage and type of buildings. These
rules make the map data well suited for GIS, allow easy plotting
of simple cartographic products, and form a map which is easy to
combine with other geographic related data.
Bornholm Project
FK-standard. In spring 1991 the Danish island of Bornholm was
covered by aerial photography scale 1:25.000 for updating the
analog map 1:25.000. This photography was used to develop the
new standard and testing the Phocus system. The test area is
approximately 600 km* and are covered by approximately 75
models. While plotting the standard developed according to in-
house wishes. The standard was called "FK-standard" because the
acronym for the plotting unit was FK. The standard was published
1993. The most sophisticated part of the standard was that more
than half the object types were defined as areas, and that build-up
areas were devided in four classes. To test how this classification
would work out in practice it was decided to plot, what was
considered the most difficult area in Denmark: the central part of
Copenhagen. This test worked out very well. To reduce plotting
time, because this time is expensive, data acquisition has to follow
the rules of the software used in the data acquisition phase.
Another point is that data created by photogrammetry are not
perfect and need revision. This is normally done in an after
processing that follows the plotting. The main scope is to correct
the data using other sources than aerial photographs and to ensure
that structure in data is correct according to the defined rules of
plotting.
TOP10DK. Having a standard for photogrammetric plotting does
not mean that a database also is defined. The specification of the
database is based on a data model which is separated in three
parts: geometric topology, semantic topology, and an object
391
catalogue. The geometric topology describes the rules for the
interrelation of the different types of geometry: point, line, and
area. All object types are connected to one of these types. The
semantic topology establishes rules for the interrelation of the
different types of objects. The object catalogue is a description of
the different types of objects of TOPIODK. This part of the
specification is very similar to the plotting standard. Besides this
the specification contains rules for how the administrative
division of Denmark has to be worked out. Rules about place
names and elevation conditions are also included in TOP10DK.
Aarhus Project
Having the standard and being quite satisfied with it the next step
was to make the standard known throughout the country. The
National Survey contracted private companies to work out test
plots. The final step was to announce a public test inviting
possible future users to participate. An area of approximately 100
km? in the northern part of Aarhus the second largest city of
Denmark was chosen. Production of data was handed out to a
private company and afterwards checked and upgraded by the
National Survey.
Governmental agencies, counties, local communities, and private
companies participated in the project. All participants had the data
and used it in their everyday life. After the test period they were
interviewed about experiences good or bad. Special interest was
payed to wishes concerning content of the database, time of
establishing and number of features, and the degree of details of
objects. A result of the Aarhus pilot test was that it was strongly
stated to the National Survey, that a complete coverage of
Denmark was the most important matter, even more important
than the number of individual codes or themes. Consequently the
standards were changed.
Additional Data. All participants expressed wishes concerning
height information. Using photogrammetry as a basic data
acquisition method all points are three dimensional from the
beginning. If the producer has to edit data height information
might be lost, but in principle all points have three coordinates. If
the basis was chosen to be older technical map data heights are not
always present. It was decided to add height information to the
data. At the National Survey there exists a DHM covering the
whole of Denmark. The grid is 50 x 50 m and the accuracy of the
points is expected to be between one and two metres. Further
contour lines with equidistance of 2.5 metres were scanned,
vectorized and annotated.
Considering a topographical database geographical place names
are important. A place name serves as a key in the database, since
the users very seldom know the coordinates of a place, but instead
they know the name. Place names have been in databases for quite
along time in Denmark. Approximately 150.000 placenames are
stored in a relational database in 20 tables. Place names and
appellatives will be connected to geometry to serve as keys in the
data base.
Denmark is completely covered by cadastral maps. Now these
maps are converted to digital form. The cadastral register has been
on EDP for several years. Combining these databases in a GIS
will form a very strong tool for administrating Denmark.
Outside the field of responsibility of the National Survey other
databases exist. Most interesting are addresses, which during the
last decade have been linked to the digital technical maps. The
linking is established through a coordinated point situated inside
the polygon of the house. Addresses are considered as a primary
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
