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$Date: 23-Sep-2001 $
$Revision: 1.30 $
$Author: Frank Naudé $
Topics
With this, representation of features (point, line or polygon) are stored in a single field within a table. A single Helical Hyperspatial code (HHCODE) is used to store the Euclidean spatial dimensions and additional data dimensional include depth, elevation, or time. The types of multidimensional data are restricted only in that they must be a numeric data type and have a bounded range. The HHCODE is generated through the recursive decomposition of dimensional space. Attribute data for specific multidimensional data is stored within columns of a table in the database. Access to the data for processing and manipulation is accomplished through extensions to Oracle PL/SQL.
Object-relational model - uses a table with single column of type MDSYS.SDO_GEOMETRY and a single row per geometry instance.
Relational model - uses a table with a predefined set of columns of type NUMBER and one or more rows for each geometry instance.
The object model provides more features. In Oracle8i, the Object model didn't support replication, partitioning and distribution. From oracle9i there is no benefits in choosing the relational model above the object model.
Oracle 9i:
SQL> connect SYS as SYSDBA
SQL> @?/md/admin/mdinst.sql
Oracle 8i:
SQL> REM # Create MDSYS users as part of the ORD (Object Relational Data)
SQL> REM # install script ordisys.sql:
SQL> connect SYS as SYSDBA
SQL> @?/ord/admin/ordisys.sql
SQL> REM # Install MD catalog into the MDSYS user
SQL> connect mdsys/mdsys
SQL> @?/md/admin/catmd.sql
Oracle 8.0:
SQLPLUS> REM # Create user MDSYS with admin option
SQLPLUS> connect SYS as SYSDBA
SQLPLUS> @?/md/install/mdsysid.sql
SQLPLUS> REM # Install MD catalog into the MDSYS user
SQLPLUS> connect mdsys/mdsys
SQLPLUS> @?/md/admin/catmd.sql
NOTE: Also run catmd.sql after upgrading to a new Oracle release.
RASTER DATA - raster (or grid cell type) data can be used for analyzing, overlaying, and modeling areal features such as soil types or forested areas. Raster data are generally typically scanned in from maps.
VECTOR DATA - vector data can be used to represent linear features such as roads, streams or area edges and can be combined with raster data for display purposes or for analysis.
In general, Raster maps are faster, Vector maps are more spesific and more accurate.
In Oracle, a HHCODE is a datatype used for both spatial indexing and partitioned point data.
More technical:
HHCodes are in effect Peano Codes, an implementation of Space Filling Curves. The multidimensionality aspect is the use of the Riemannian hypercube in conjunction with the space filling curve. What in effect has happened is that the Riemannian tensor matrix has been mapped by the space filling curve. This gives mathemetical credence to HHCodes and a lot more functionality then just data access. One more thing the HHcode encoding is not just Euclidean, Curvilinear and linear coordinates such as Lat, Lon, depth and time can also be mapped together. This creates Time varying voxels, (I suppose one can call them toxels).
Contributed: Herman Varma
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