—"
text, if aligned with topography left bottom (1b)
(second point for data transfer to be calculated
by length and rotation angle of the text)
symbol, if parallel to grid center center (cc)
symbol, if aligned with topography ^ center center (cc)
(azimuth to be calculated form rotation angle)
For a number of features, there is the possibility of using
OSKA 0292 - an arrow -, if the space is not sufficient for
placing the feature in the required position, e.g. a parcel
number inside a parcel, the head of the arrow serves then as
object coordinate, while the ending has to coincide with the
text origin of the text, (here: parcel number). For the head of
the arrow, the MicroStation command ‘line terminator’ is
going to be used, which requires a cell to be placed at the end
of a line.
As the usual work-flow implies the other possible sequence of
points (from the text to the area), an ucm was programmed, in
order to exchange the sequence of points in the linear part of
the arrow by calling the new MicroStation feature ‘change
direction of a line' already during placement.
Object names
Alpha-numerical information, mostly
annotations, etc., requested as ‘Objektname’
are stored using the MicroStation feature ‘tag’.
‘Tag’ is a simple, non-hierarchical database with user-defined
tables, called ‘tag sets’. The single entries represent the data to
be attached to geometric elements. These entries can either
have default or individual values. Another possibility is the
‘displayable tag’, where the value can be placed as text in the
MicroStation design file.
object names,
- „object name“
Examples for tags are:
object name of a parcel, here the information on
cadastral division and sub-division is stored
annotation of man holes, here the usage (e.g. electricity,
sewerage, telephone) is shown as a displayable tag.
Área coverage
Two layers of the ALK have to be captured with full area
coverage (parcels and actual land use). The completeness of
the procedure can be checked by area calculation. The sum of
the single areas has to be equal to the total area size.
MicroStation offers possibilities of creating shapes (closed
areas) around centroids (e.g. text, cell, etc.) and area
calculation of these shapes. Before an automatic creation of
shapes can be performed, the geometry (over- and undershoots,
etc.) has to be checked. This is also required as a quality check
[ZV-Aut 1994, p.7]. Standard software for this is available
(e.g. MGE, MircoGIS).
Also for other area objects such as buildings, roads and
embankments, a centroid is going to be placed (e.g. parcel
number, OSKA-code, embankment symbol, etc.). The shapes
to be created for this features can consist of elements from
several levels. A list of relevant levels has to be assigned to
specific features.
Checking the complete area coverage can be done in two ways:
either by using a data base for the storage of parcel sizes
and calculation of sums
orby annotating every complex shape with its size,
extracting these in an ASCII-file (mdl TEXTX) and
839
using this as entry to EXCEL (chart calculation
program).
In both cases, the result has to be compared with the size of the
complete area captured.
The method last described should be supported by a mdl,
combining the single steps.
The error detection (e.g. missing areas, etc.) can be supported
by using the area fill (display function) for shapes.
Symbols
Within the ZV-Aut NRW the layout of every feature to be
captured is given. By listing line width, text size and style,
symbol size and default offset (where applicable) for every
item, combined with an example, a complete definition is
given for the cartographic layout.
A large number of ALK objects are shown as point symbol, e.g.
parcel boundary marker, man hole, symbols for actual land use,
etc..
There are two possibilities within MicroStation to create point
symbols: cells or symbol fonts. Although cell are the default
way, symbol fonts offer a number of advantages in terms of
less storage requirements, easier updating a data set after
applying changes and protection against unwanted changes,
therefore this possibility was chosen.
Line styles
Within the ZV-Aut NRW, also a large variety of linear
symbolization is defined. From cadastral boundaries and ferry
routes as dashed lines in different variations of line styles and
gaps, to hedges, fences and metro lines as combinations of
lines and symbols. There are about forty different line styles.
Employing the new MicroStation command 'custom line style’,
a line style library was established, trying to fulfil] the
requirements of the ZV-Aut NRW.
Special attention was paid to the feature ‘hedge’, where the
specification defines the opening of the circular symbol to be
always heading south, disregarding the orientation of the base
line. This could not be achieved with a satisfactory result.
non-redundancy of the data set
The most complex problem to be tackled is the non-
redundancy. Out of several possibilities (color-coding,
attaching a database, using tags, storing the OSKA-code as z-
value, redundant capturing) the last possibility was chosen. As
the data input is inhomogenous, the multi-theme lines are not
easy to recognize during data capturing procedures already. For
the work flow, this solution has only minor drawback.
For data transfer, redundant data can be delivered via EDBS
using the parameter FEIN. The target system has to take care,
if an element is new or already stored in the database. If the
object already exists, only the new OSKA-code has to be
assigned [Steinbach 1995].
6. Practical test
A practical test was performed in order to verify the
possibilities of the data structure and user-interface designed.
For the sake of realistic conditions, a test side in Germany was
chosen. Due to personal contacts, a cooperation with the
cadastral office of Wuppertal could be arranged. Aerial
photographs and cadastral maps were supplied. The test was
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
