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A subdevision of the LVermA BB called "Topographischer
Meldedienst" (TopMD, topographical information service) will
get a key-function for updating and extension of the DLM 25.
Up to now the main task of the TopMD was to acquire and
prepare non-geometric descriptive information for the
revision of the TK 10 and derived maps (e.g. city maps).
In contrast to the OK-DLM 25/1 the object catalogue
OK-DLM 25/2 contains a lot of objects and attributes which
can not be captured from orthophotos or existing maps. The
new task of the TopMD is to get into contact with suppliers of
these informations and prepare them for updating and
revision of the DLM 25. In a first stage up to the end of 1997
these information will be transferred into film plots of existing
DLM 25/1 data in a colour coded form. An information
system based on ARC/Info has been installed in 1995 for
taking over and storing of the informations in digital form.
3.3 Improvement of Planimetric Accuracy
In the western part of Germany the German Basic Map
1 : 5,000 (DGK 5) is used as primary data source for
establishing the DLM 25/1. Per definition the planimetric
accuracy of the DGK 5 should be + 3 m or better. This meets
exactly the ATKIS requirement for the DLM 25. In the new
federal states of the eastern part of Germany only
topographaphic maps 1 : 10,000 (TK 10 AS) were available.
For the area of Brandenburg these maps were generated
from 1956 to 1973 mainly on the basis of rectified aerial
photographs. Meanwhile - after 5 revision cycles - the
planimetric accuracy is about + 5 - 10 m (Krakau, 1994). In
1992 the LVermA BB has started a program to convert the
TK 10 AS (Krassowski, A\= 3.75' x Aq» 2.5!) into the new TK
10 N map series (Bessel, AX» 5' x Aq» 3"). While doing this,
the planimetric accuracy will not be improved. The
conversion program will be completed in 1998.
When the conception for creating the DLM 25/1 in
Brandenburg was worked out, it has been decided, that a
fast completition is of greater importance than meeting the
accuracy requirement.
In areas where the TK 10 N was not yet available orthophoto
maps 1 : 10,000 (TK 10 L) were used as primary data
source. These orthophoto maps were generated in contract
by private companies mainly by simple rectification without
using a digital elevation model (DEM). In general Branden-
burg is a rather flat area, but for some map sheets the effect
of neglecting the relief generated local positional errors of up
to 15 m.
Since November 1994 the LVermA BB is able to produce
orthophoto maps 1 : 10,000 (TK 10 DL) by digital image
processing with the Zeiss/PHODIS-system. Tests have
Shown that DLM 25/1 data captured from this source will
meet the accuracy requirement of + 3 m. The same is true for
DLM 25/1- data acquired by stereo compilation.
The limited planimetric accuracy of most of the DLM 25/1
data becomes a problem if these data shall be merged with
data from other (more accurate) sources, e.g. geodetic
measurements. This could be the case if
- the LVermA BB wants to incorporate data into the DLM
25, e.g. buildings extracted from the ALK (the axis of a
road may pass through buildings),
- Users want to add their own thematic data, e.g. utility
companies want to add their network of power lines (a
road may cross a power line several times instead of
running in parallel).
583
Since the number of DLM 25 users ist constantly growing,
the planimetric accuracy should be improved as soon as
possible. The correction of geometry can be done
independently from updating and extension to the DLM 25/2
using digital orthophotos or by stereo-compilation.
Tests have shown that the geometric displacements are
more or less random. Therefore the problem can not be
solved with a semi-automatic procedure, e.g. a batch
program. However the GIAP software supports manual
editing such that points can be picked and moved to the right
position without destroying the topology of the data. Tests
have also shown that only about 1/3 of the points have to be
shifted (e.g. points of the boundaries of built-up areas don't
need to be shifted because these boundaries can not be
sharply defined).The work for improving the planimetric
accuracy will be started in April 1996.
3.4 Use of Digital Orthophotos
In 1993 a PHODIS-system (Photogrammetric Digital
System) from Zeiss was installed at the LVermA BB for digital
production of orthophoto maps. The system consists of a
PS1 photogrammetric scanner, three workstations running
the PHODIS-software and the SCOP/DEM-software, an IRIS
3047 colour proofer and a BARCO BG3800 raster scanner/
plotter. In November 1994 the system became operational.
The production rate is up to 8 orthophoto maps 1 : 10,000
per day (8 h). In October 1995 a PHODIS ST 30 digital
stereoworkstation was integrated into the system. It is mainly
used for DEM measurement and DEM control.
The digital orthophotos are produced from b&w aerial
photographs 1 : 34,000. As a preprocessing step a DEM 25
is generated from digitized contours of topographic maps 1 :
25,000 and additional stereo-scopic measurements in areas
with non-uniform relief. The grid width is 25 m x 25 m. The
accuracy of the DEM is about + 2 m. The output format for
the orhophotos is TIFF. The ground resolution of an
orthophoto pixel is 65 cm x 65 cm.
Tests have shown that the resolution and accuracy of the
orthophotos are suitable for updating and extension of the
DLM 25.
The digital orthophotos can be used with the "Raster-
Module" of the ALK-GIAP workstations. The ALK-GIAP
(Graphics Interactive Workplace) was developed by the state
survey administration of Northrhine-Westfalia for interactiv
and graphic aided work with data of the ALK. Later on the
software system was extended to handle the ATKIS data
structure. On the basis of this software AED Graphics has
created an all-purpose geo-information system. Currently
seven GIAP workstations with Raster-Module and connection
to a table digitizer are available at the LVermA BB for
correction, updating and extension of the DLM 25.
A digital orthophoto can be loaded into the GIAP, displayed
and overlayed with DLM 25 vector data. The display of raster
or vector data can be switched off. Different transparent and
opaque modes are also available. At the moment the display
of orthophotos is limited to 64 gray values. This figure has to
be increased for reliable interpretation.
For detection of changes and new DLM 25/2-objects the
following alternatives will be tested concerning reliability and
production speed :
a) Overlaying a raster plotter output of the digital orthophoto
and a plot of the DLM 25/1 vector data on a light table
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
