corresponding components: other ’less’ complex
objects and/or primitive elements which compose
this complex object.
- Map elements: a set of topologically related map
elements: Nodes /Lines/ Polygons), which provide
the spatial descriptions of Theme Objects.
The primitive elements which are related to all
Theme-objects in one Data Theme-Group are
grouped in one ’pool’, referred to as Theme 0.
This will preserve the topology between the
spatial objects on both levels: in the theme as
well as across themes.
The semantic descriptors of terrain objects are
given as a set of values for a given Attribute
List which is defined in the Transfer’s Data
Dictionary. Two sets of attributes can be assigned
to theme’s objects: Standard Set (defined by the
specifications), and Non-Standard Set (defined in
agreement with the receiving agency).
The structure of this Transfer in the physical
volumes, as shown in figure (1), has the following
schema:
SET (1): Transfer Global Information Records:
Administrative aspects, definition and area
coverage, Data Dictionary.
SET (2): Area-Tile Records:
Definition, area coverage and description of
contents, spatial coordinate reference, overall
evaluation for the data quality.
SET (3): Theme-Group Records:
Definition of the Theme-Group and list of the
Themes included.
SET (4): Theme Records:
1. Definition of the Theme and the type of its
objects.
2. Definition of Theme's Entity-Types
(sub-classes) and definition of their objects
attributes.
3. Theme-Object Lists (object identifiers,
quality parameters, attribute lists and
reference to their spatial components (other
objects and/or map elements).
Elements Records
Coordinates and
SET (5): Primitive Map
(Nodes/Points, Lines, Areas)
topology of these elements.
Further details are given in the Appendix.
COMPUTER PACKAGES FOR DATA CONVERSION
The development of standards for the exchange of
digital data includes the design of 'interfaces'
between the proposed standard and the various GIS
systems. These include procedures and computer
packages for the conversion of the data files in
these systems to the Standard Format, and vice
versa.
The effort and time needed for this task should
not be under estimated and it might exceed the
benefits for their specialist applications. Its
complexity vary according to the nature of the
internal data structure of the database in
comparison with those of the proposed Standard.
Subset or ‘profiles’ of the proposed standard may
therefore be required to simplify implementation
for particular applications.
Within the framework of the first prototype
development, two computer packages
(ARCINFO TO BAKO and BAKO TO ARCINFO) were
234
developed for the conversion of terrain
information (organization, locations and
attributes of terrain features), in the ARC/INFO
files (where the Bakosurtanal Database is
resident) into the proposed Standard Format and
vice versa. At this stage of development, these
programs are based on a simplified ‘profile’ of
the proposed Standard, and are subject to
modification and expansion. The objectives of
these packages are:
- provide a tool for the exchange data files,
extracted from the Bakosurtanal Database, to
other agencies which are taking part in the
testing of the first prototype.
- give an example to follow in order to help BPPT
in developing further ‘interfaces’ between this
Standard and other available GIS systems in
Indonesia.
The program package ARCINFO TO BAKO consists of
various modules which are executed in a similar
sequence to that in Figure (1). The tasks of these
modules is to process the information stored in
the Bakosurtanal Topographic Database in the
ARC/INFO MAPLIBRARY files, [5], and organize them
in the required data structure and format:
- Information about the organization of the
terrain features in Area-Tiles, Theme-Groups,
Themes and Theme's Entity-Types and
Theme-Objects will be obtained from the
MAPLIBRARY DATABASE MANAGEMENT Files and used to
write the data sets: SET (1), SET (2), SET (3),
SUB-SET (4.1), SUB-SET (4.2).
- Semantic descriptors (Attributes) of themes
objects vill be obtained from the INFO and other
related Databases Files and used to write the
data Set: SUB-SET (4.3).
- Spatial descriptors (location and topology) of
the theme’s objects will be defined by the basic
map elements (Nodes, Points, Lines, Areas).
These elements are described by their location
(coordinates) and the topological relationships
amongst them and obtained from ARC/INFO Files
(ARC, PAL, CNT, LAB, AAT, PAT}, in. order to
write the data set: SET (5).
The program package BAKO TO ARCINFO will process
the information encoded in the Transfer and
organize them in ARC/INFO coverages and INFO
files:
- Information in data sets: SET (1), SET (2),
SET - (3), SUB-SET (4.1), SUB-SET (4.2)' are
organized in the MAPLIBRARY DATABASE MANAGEMENT
Files.
- Information in data set: SUB-SET (4.3) about
object attributes are stored in INFO Tables,
ARC/INFO Coverage-wise, and the references to
map elements in SET (5) are used to pick up the
corresponding elements which form the Theme’s
objects and stored in ARC/INFO Files (ARC, PAL,
CNT, LAB, AAT, PAT).
Note: complex objects (formed from 'less' complex
ones) are not considered in this version and
only a simplified profile of this Standard is
considered for the transfer of topologically
structured vector data.
These modules were written in FORTRAN Language and
use the various subroutines in the ARC/INFO
Programmer Library in order to access various data
files in ARC/INFO, [1].
FUTURE DEVELOPMENT
In the next phase of the LREP Project, 1992-1996,
the task of testing and upgrading the proposed
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