inania >
Topological data types include AREA (closed polyline),
LINE (open polyline), POINT (single point) and WINDOW
(rectangle parallel to coordinate system axis). Additional
operators (.X. , .«. , .». , ...) allow for intersection and
selection of geometric/topological data sets.
Communication between TOPDB and an application is
done by a data base language called ,TOPSQL Its
current functionality is on the one hand a subset of ANSI-
SQL but on the other hand an extension regarding the
geometric/topological data types and operators.
A typical data selection could be to extract all data from a
specified table, which are at least partly inside a given
area, which have an accuracy for heights better than 30
cm and have been compiled later than 1985-10-20.
These query can be formulated by using TOPSQL.
SELECT * FROM DHMDATA
WHERE (COORDINATES .X. AREA (10000 50000
15000 60000
20000 40000)
AND (ZACCURACY « 0.30)
AND (COMPILEDATE » 20.10.1985);
5.3 Table System
For storing, managing and archiving topographic data a
complex system of tables is used. Several types of
different tables have been defined to describe the
structure of a table and the data type for each column of
the table. In SCOP.TDM about two dozens of different
table types are involved. Most of them serve only for
internal organizational or summary purposes, but a few
of them are of interest for the user. This includes tables
for storing topographic data, tables for controlling
translation of coding information during data import and
export and vocabulary tables.
5.3.1 Tables for Storage of Topographic Data: The
most important tables are of type TDXYZTAB. Such
tables are used to store and manage arbitrarily
distributed topographic data. A data set in one of these
tables corresponds to exactly one terrain object
represented by a series of 3-dimensional coordinates and
additional data properties. The full definition of a table of
type TDXYZTAB is shown in table 1.
IDOBJ INTEGER UNIQUE INDEX NOT NULL SYSNUM
IDENTIFIER
DATAFORMAT CHAR (16) INDEX NOT NULL
AGGREGATE CHAR (16) INDEX NOT NULL
OBJECTNAME CHAR(16) INDEX NOT NULL
OBJECTTYPE CHAR(16) INDEX NOT NULL
COORDINATES LINE INDEX NOT NULL PERIOD(3)
RESOLUTION(2,2,2)
FEATURECODE CHAR(32) INDEX NULL
STATUS CHAR(16) INDEX NULL
XYACCURACY NUMBER (12.2) INDEX NULL
ZACCURACY NUMBER (12.2) INDEX NULL
CREATOR CHAR (32) INDEX NULL
OWNER CHAR (32) INDEX NULL ARRAY
COMPILEMODE CHAR (32) INDEX NULL
PROPERTIES CHAR(32) INDEX NULL ARRAY
COMPILEDATE DATE INDEX NULL
COMPILETIME TIME INDEX NULL
INSERTDATE DATE INDEX NOT NULL
INSERTTIME TIME INDEX NOT NULL
UPDATEDATE DATE INDEX NULL
UPDATETIME TIME INDEX NULL
Table 1: Definition of Table Type TDXYZTAB
For each column the name of the column, the data type,
indexing instructions and other attributes are listed. This
definition includes a list of coordinates (COORDINATES),
an object meaning (FEATURECODE), the type of an
object (OBJECTTYPE), an object name (OBJECT-
NAME), the objects original data format (DATA-
FORMAT), information about accuracy in planimetry and
height (XYACCURACY, ZACCURACY), the name of the
organization responsible for data compilation
(CREATOR), a list of authorized data users (OWNER),
information about the compilation method (COMPILE-
MODE), a list of additional properties (PROPERTIES)
and information about date and time of data compilation
(COMPILEDATE, COMPILETIME).
5.3.2 Data Format Code Conversion Tables: Topo-
graphic data are read in from files organized according to
commonly used data formats (WINPUT, DXF, ARC/INFO
Generate, ...) and are stored in topographic data tables.
This process is called ,data import". The opposite
operation is to extract data from topographic data tables
and to write these data to files. This is called ,data
export".
In both cases it is necessary to translate coding
information from the external data representation format
to the native representation and vice versa. These
translations are controlled by data format code
conversion tables, which are set up by the user. The
structure of a data format code conversion table depends
on the individual data format. Table 2 gives an example
for DXF. During the IMPORT process the coding pair for
an object in DXF (LAYER, ENTITY) is mapped to a pair
used in tables of type TDXYZTAB (FEATURECODE,
OBJECTTYPE). When exporting data the reverse
mapping is done.
IDCDXF INTEGER UNIQUE INDEX NOT NULL SYSNUM
IDENTIFIER
FEATURECODE CHAR(32) INDEX NOT NULL
OBJECTTYPE CHAR (16) INDEX NOT NULL
ENTITY CHAR (12) INDEX NOT NULL
LAYER CHAR (32) INDEX NOT NULL
COMMENT STRING NULL
162
Table 2: Definition of Table Type CVDXFTAB
5.3.3 Vocabulary Tables: On many occasions assign-
ment of names or other terms is necessary when using
SCOP.TDM. Examples are names of authorized data
users, names of coordinate systems or feature codes. To
ensure a systematic usage of such names, a global
name space can be set up in vocabulary tables as basis
for checking user input. Furthermore consistency in
spelling and using names is advantageous when
specifying conditions for data selection.
5.4 Topographic Data Market and Archive
All tables for storing topographic data together with meta-
information and additional organizational and summary
tables are placed in a disk area, which is called
„Topographic Data Market“. This area is permanently
available on the disk. It is the market place for all
activities concerning data import and data export. DTM
application programs may access these data too.
Long-term storage and archiving of topographic data is
done in the ,Topographic Data Archive". Topographic
data can either be copied or moved from the data market
to the data archive .
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
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