sequential files with x,y,z-coordinates of breaklines and
other geomorphological information.
IL Ry Y2 45 1 44
21 By 9*2. *3 74
Figure 6: GRID data organization
3.3. HYBRID data organization
Hybrid data structures make use of the advantage of
regular data organization on the different modes of
triangulation. In order to have easy data access the grid
organization is to prefer being dominant; the result is
that the hull nodes of the triangulation are nodes of the
grid. Figure 7 gives an example for the structure HY-
BRID, in which the triangles are organized with respect
to edges.
exe
TIN ) TIN
nodes zr y z edges B-node E-node
101 | zi Yıoı Z0 a 1,1 1,2
b 101 1.2
C 101 1,1
GRID d 2,2 1,2
dissi. 3 e d 101
1 Zu Z3 Z3 f 29 2.1
2 2231: 223 1233 g 101 2,1
3 231 232 233 h 1,1 21
Figure 7: HYBRID data organization
3.4. Overall data organization
In some cases it is desirable to have an overall data
organization especially for the handling of a large
amount of data. In this overall organization a contiguous
geographic region is splitted into subregions (level 1).
This subregions (cells) can be of fixed or variable size.
Every subregion may again be subdivided into sub-sub-
regions (level 2) and so on (level n) leading to a hierar-
chic data path (figure 8). This overall organization cares
for fast access of regions of special interest. A DTM
program package which realized such a data organiza-
tion is the HIFI package (Düsedau et al.,1987).
level 1
d SS
EN
Gi cn
/
Figure 8: Overall data organization
A
level 2
3
level 3
q/
4. MERGING DTM WITH GIS
4.1. Strategies for DTM integration
When merging terrain data with situation data of a GIS
three models can be applied which are realized to some
extend in practice. In all three cases the topology within
the GIS data model is a two-dimensional one.
4.1.1. Height attributing
In this case it is posssible to add heights to all existing
situation data. But this very simple approach has two
main disadvantages:
- incomplete height description; there don't exist
height data for all situation data, in general.
- dependent on the density of planimetry.
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