[Geowanking] Storing Simple Geometries in a RDBMS Model
lblake at ksninc.com
Fri Nov 30 10:53:25 PST 2007
I've got a friend from work whose is currently taking a course on
spatial database design for his GIS Certificate Program. We've recently
had some interesting discussion about spatial databases, and on the
different techniques to integrate spatial data into a traditional RDBMS.
I believe one of the challenges solved by some GIS software is the
storage of geometry objects (spatial data) in a RDBMS. (Its like trying
to fit a square peg in a round hole.) PostGIS and ESRI's Personal
Geodatabase are a couple of examples that come to mind. In most of these
implementations I believe the geometry object is stored in a single
field of a database table as a BLOB or a text string that can be parsed
by the spatial database engine for processing of spatial queries.
What are the limitations or technical challenges that come from a
different approach, that of storing feature geometries in a database
using the traditional relational database model?
A database has a Coordinates table which stores a unique id for each
coordinate, with a northing, easting, and elevation. The database has
another Line table which stores a unique id and perhaps the length of
the line. A third PointsToLines table stores entries that link
Coordinates to Lines using the unique ids in both tables. Queries could
then be executed to obtain all the coordinates that make up a line, for
Is there a reason why this technique is not used more frequently? Is
there popular software that does use this technique to store spatial
Thanks for your thoughts.
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